People can distinguish 150 to 200 main colors and seven million different colors {vision, color} {color vision}, by representing the light intensity-frequency spectrum and separating it into categories.
color: spectrum
Colors range continuously from red to scarlet, vermilion, orange, yellow, chartreuse, green, spring green, cyan, turquoise, blue, indigo (ultramarine), violet, magenta, crimson, and back to red. Scarlet is red with some orange. Vermilion is half red and half orange. Chartreuse is half yellow and half green. Cyan is half green and half blue. Turquoise is blue with some green. Indigo is blue with some red. Violet is blue with more red. Magenta is half blue and half red. Crimson is red with some blue.
color: definition
Blue, green, and yellow have definite wavelengths at which they are pure, with no other colors. Red has no definite wavelength at which it is pure. Red excites mainly long-wavelength receptor. Yellow is at long-wavelength-receptor maximum-sensitivity wavelength. Green is at middle-wavelength-receptor maximum-sensitivity wavelength. Blue is at short-wavelength-receptor maximum-sensitivity wavelength.
color: similarities
Similar colors have similar average light-wave frequencies. Colors with more dissimilar average light-wave frequencies are more different.
color: opposites
Complementary colors are opposite colors, and white and black are opposites.
color: animals
Primates have three cone types. Non-mammal vertebrates have one cone type, have no color opponent process, and detect colors from violets to reds, with poorer discrimination than mammals.
Mammals have two cone types. Mammals have short-wavelength receptor and long-wavelength receptor. For example, dogs have receptor with maximum sensitivity at 429 nm, which is blue for people, and receptor with maximum sensitivity at 555 nm, which is yellow-green for people. Mammals can detect colors from violets to reds, with poorer discrimination than people.
With two cone types, mammals have only one color opponency, yellow-blue. Perhaps, mammals cannot see phenomenal colors because color sensations require two opponent processes.
nature: individuality
People's vision processes are similar, so everyone's vision perceptions are similar. All people see the same color spectrum, with the same colors and color sequence. Colorblind people have consistent but incomplete spectra.
nature: objects
Colors are surface properties and are not essential to object identity.
nature: perception
Colors are not symmetric, so colors have unique relations. Colors cannot substitute. Colors relate in only one consistent and complete way, and can mix in only one consistent and complete way.
nature: subjective
No surface or object physical property corresponds to color. Color depends on source illumination and surface reflectance and so is subjective, not objective.
nature: irreducibility
Matter and energy cannot cause color, though experience highly correlates with physical quantities. Light is only electromagnetic waves.
processes: coloring
Three coloring methods are coloring points, coloring areas, or using separate color overlays. Mind colors areas, not points or overlays, because area coloring is discrete and efficient.
processes: edge enhancement
Adjacent colors enhance their contrast by adding each color's complementary color to the other color. Adjacent black and white also have enhanced contrast.
processes: timing
Different color-receptor-system time constants cause color.
processes: precision
People can detect smaller wavelength differences between 500 nm and 600 nm than above 600 nm or below 500 nm, because two cones have maximum sensitivities within that range.
physical: energy and color
Long-wavelength photons have less energy, and short-wavelength photons have more energy, because photon energy relates directly to frequency.
physical: photons
Photons have emissions, absorptions, vibrations, reflections, and transmissions.
physical: reflectance
Color depends on both illumination and surface reflectance [Land, 1977]. Comparing surface reflective properties to other or remembered surface reflective properties results in color.
physical: scattering
Blue light has shorter wavelength and has more refraction and scattering by atoms.
Long-wavelength and medium-wavelength cones have similar wavelength sensitivity maxima, so scattering and refraction are similar. Fovea has no short-wavelength cones, for better length precision.
mixing
Colors from light sources cannot add to make red or to make blue. Colors from pigment reflections cannot add to make red or to make blue.
properties: alerting and calming colors
Psychologically, red is alerting color. Green is neutral color. Blue is calming color.
properties: contraction and expansion by color
Blue objects appear to go farther away and expand, and red objects appear to come closer and contract, because reds appear lighter and blues darker.
properties: color depth
Color can have shallow or deep depth. Yellow is shallow. Green is medium deep. Blue and red are deep.
Perhaps, depth relates to color opponent processes. Red and blue mainly excite one receptor. Yellow and green mainly excite two receptors. Yellow mixes red and green. Green mixes blue and yellow.
properties: light and dark colors
Yellow is the brightest color, comparable to white. In both directions from yellow, darkness grows. Colors darken from yellow toward red. Colors darken from yellow toward green and blue. Green is lighter than blue, which is comparable to black.
properties: sad and glad
Dark colors are sad and light colors are glad, because dark colors are less bright and light colors are more bright.
properties: warm and cool colors
Colors can be relatively warm or cool. Black-body-radiator spectra center on red at 3000 K, blue at 5000 K, and white at 7000 K. Light sources have radiation surface temperature {color temperature} comparable to black-body-radiator surface temperature. However, people call blue cool and red warm, perhaps because water and ice are blue and fires are red, and reds seem to have higher energy output. Warm pigments have more saturation and are lighter than cool pigments. White, gray, and black, as color mixtures, have no net temperature.
properties: hue change
Colors respond differently as hue changes. Reds and blues change more slowly than greens and yellows.
factors
Colors change with illumination intensity, illumination spectrum, background surface, adjacent surface, distance, and viewing angle. Different people vary in what they perceive as unique yellow, unique green, and unique blue. The same person varies in what they perceive as unique yellow, unique green, and unique blue.
realism and subjectivism
Perhaps, color relates to physical objects, events, or properties {color realism} {color objectivism}. Perhaps, color is identical to a physical property {color physicalism}, such as surface spectral reflectance distribution {reflectance physicalism}. Perhaps, colors are independent of subject and condition. Mental processes allow access to physical colors.
Perhaps, colors depend on subject and physical conditions {color relationism} {color relativism}.
Perhaps, things have no color {color eliminativism}, and color is only in mind. Perhaps, colors are mental properties, events, or processes {color subjectivism}. Perhaps, colors are mental properties of mental objects {sense-datum, color}. Perhaps, colors are perceiver mental processes or events {adverbialism, color}. Perhaps, humans perceive real properties that cause phenomenal color. Perhaps, colors are only things that dispose mind to see color {color dispositionalism}. Perhaps, colors depend on action {color enactivism}. Perhaps, colors depend on natural selection requirements {color selectionism}. Perhaps, colors depend on required functions {color functionalism}. Perhaps, colors represent physical properties {color representationalism}. Perhaps, experience has color content {color intentionalism}, which provides information about surface color.
Perhaps, humans know colors, essentially, by experiencing them {doctrine of acquaintance}, though they can also learn information about colors.
Perhaps, colors are identical to mental properties that correspond to color categories {corresponding category constraint}.
Properties {determinable property} can be about categories, such as blue. Properties {determinate property} can be about specific things, such as unique blue, which has no red or green.
Perhaps, there are color illusions due to illumination intensity, illumination spectrum, background surface, adjacent surface, distance, and viewing angle. Human color processing cannot always process the same way or to the same result. Color names and categories have some correspondence with other animals, infants, and cultures, but vary among scientific observers and by introspection.
How can colors be in mind but appear in space? Subjectivism cannot account for the visual field. Objectivism cannot account for the color facts.
Differences among objective object and physical properties, subjective color processing, and relations among surfaces, illumination, background, viewing angle and distance do not explain perceived color differences {explanatory gap, color}.
White, gray, and black have no hue {achromatic} and have color purity zero.
Color can have no definite depth {aperture color}, such as at a hole in a screen.
If eyes completely adapt to dark, people see gray {brain gray} {eigengrau}.
Each opponent system has a relative response for each wavelength {chromatic-response curve}. The brightness-darkness system has maximum response at 560 nm and is symmetric between 500 nm and 650 nm. The red-green system has maximum response at 610 nm and minimum response at 530 nm and is symmetric between 590 nm and 630 nm and between 490 nm and 560 nm. The blue-yellow system has maximum response at 540 nm and minimum response at 430 nm and is symmetric between 520 nm and 560 nm and between 410 nm and 450 nm.
Sight tries to keep surface colors constant {color constancy}. Lower luminance makes more red or green, because that affects red-green opponency more. Higher luminance makes more yellow or blue, because that affects blue-yellow opponency more.
Light polarization can affect sight slightly {Haidinger brush}.
Color relates directly to electromagnetic wave frequency {color, frequency} and intensity.
frequency
Light waves that human can see have frequencies between 420 and 790 million million cycles per second, 420 and 790 teraHertz or THz. Frequency is light speed, 3.02 x 10^8 m/s, divided by wavelength. Vision can detect about one octave of light frequencies.
frequency ranges
Red light has frequency range 420 THz to 480 THz. Orange light has frequency range 480 THz to 510 THz. Yellow light has frequency range 510 THz to 540 THz. Green light has frequency range 540 THz to 600 THz. Blue light has frequency range 600 THz to 690 THz. Indigo or ultramarine light has frequency range 690 THz to 715 THz. Violet light has frequency range 715 THz to 790 THz. Colors differ in frequency range and in range compared to average wavelength. Range is greater and higher percentage for longer wavelengths.
Reds have widest range. Red goes from infrared 720 nm to red-orange 625 nm = 95 nm. 95 nm/683 nm = 14%. Reds have more spread and less definition.
Greens have narrower range. Green goes from chartreuse 560 nm to cyan 500 nm = 60 nm. 60 nm/543 nm = 11%.
Blues have narrowest range. Blue goes from cyan 480 nm to indigo or ultramarine 440 nm = 40 nm. 40 nm/463 nm = 8%. Blues have less spread and more definition.
wavelength ranges
Spectral colors have wavelength ranges: red = 720 nm to 625 nm, orange = 625 nm to 590 nm, yellow = 590 nm to 575 nm, chartreuse = 575 nm to 555 nm, green = 555 nm to 520 nm, cyan = 520 nm to 480 nm, blue = 480 nm to 440 nm, indigo or ultramarine = 440 nm to 420 nm, and violet = 420 nm to 380 nm.
maximum purity frequency
Spectral colors have maximum purity at specific frequencies: red = 436 THz, orange = 497 THz, yellow = 518 THz, chartreuse = 539 THz, green = 556 THz, cyan = 604 THz, blue = 652 THz, indigo or ultramarine = 694 THz, and violet = 740 THz.
maximum purity wavelengths
Spectral colors have maximum purity at specific wavelengths: red = 683 nm, orange = 608 nm, yellow = 583 nm, chartreuse = 560 nm, green = 543 nm, cyan = 500 nm, blue = 463 nm, indigo or ultramarine = 435 nm, and violet = 408 nm. See Figure 1. Magenta is not spectral color but is red-violet, so assume wavelength is 730 nm or 375 nm.
maximum sensitivity wavelengths
Blue is most sensitive at 482 nm, where it just turned blue from greenish-blue. Green is most sensitive at 506 nm, at middle. Yellow is most sensitive at 568 nm, just after greenish-yellow. Red is most sensitive at 680 nm, at middle red.
color-wavelength symmetry
Colors are symmetric around middle of long-wavelength and middle-wavelength receptor maximum-sensitivity wavelengths 550 nm and 530 nm. Wavelength 543 nm has green color. Chartreuse, yellow, orange, and red are on one side. Cyan, blue, indigo or ultramarine, and violet are on other side. Yellow is 583 - 543 = 40 nm from middle. Orange is 608 - 543 = 65 nm from middle. Red is 683 - 543 = 140 nm from middle. Blue is 543 - 463 = 80 nm from middle. Indigo or ultramarine is 543 - 435 = 108 nm from middle. Violet is 543 - 408 = 135 nm from middle.
Cone outputs can subtract and add {opponency} {color opponent process} {opponent color theory} {tetrachromatic theory}.
red-green opponency
Middle-wavelength cone output subtracts from long-wavelength cone output, L - M, to detect blue, green, yellow, orange, pink, and red. Maximum is at red, and minimum is at blue. See Figure 1. Hue calculation is in lateral geniculate nucleus, using neurons with center and surround. Center detects long-wavelengths, and surround detects medium-wavelengths.
blue-yellow opponency
Short-wavelength cone output subtracts from long-wavelength plus middle-wavelength cone output, (L + M) - S, to detect violet, indigo or ultramarine, blue, cyan, green, yellow, and red. Maximum is at chartreuse, minimum is at violet, and red is another minimu is at red. See Figure 1. Saturation calculation is in lateral geniculate nucleus, using neurons with center and surround. Luminance output goes to center, and surround detects short-wavelengths [Hardin, 1988] [Hurvich, 1981] [Katz, 1911] [Lee and Valberg, 1991].
brightness
Long-wavelength and middle-wavelength cones add to detect luminance brightness: L + M. See Figure 1. Short-wavelength cones are few. Luminance calculation is in lateral geniculate nucleus, using neurons with center and surround. Center detects long-wavelengths, and surround detects negative of medium-wavelengths. Brain uses luminance to find edges and motions.
neutral point
When positive and negative contributions are equal, opponent-color processes can give no signal {neutral point}. For the L - M opponent process, red and cyan are complementary colors and mix to make white. For the L + M - S opponent process, blue and yellow are complementary colors and mix to make white. The L + M sense process has no neutral point.
color and cones
Red affects long-wavelength some. Orange affects long-wavelength well. Yellow affects long-wavelength most. Green affects middle-wavelength most. Blue affects short-wavelength most.
Indigo or ultramarine, because it has blue and some red, affects long-wavelength and short-wavelength. Violet, because it has blue and more red, affects long-wavelength more and short-wavelength less. Magenta, because it has half red and half blue, affects long-wavelength and short-wavelength equally. See Figure 1.
White, gray, and black affect long-wavelength receptor and middle-wavelength receptor equally, and long-wavelength receptor plus middle-wavelength receptor and short-wavelength receptor equally. See Figure 1. Complementary colors add to make white, gray, or black.
color and opponencies
For red, L - M is maximum, and L + M - S is maximum. For orange, L - M is positive, and L + M - S is maximum. For yellow, L - M is half, and L + M - S is maximum. For green, L - M is zero, and L + M - S is zero. For blue, L - M is minimum, and L + M - S is minimum. For magenta, L - M is half, and L + M - S is half.
saturation
Adding white, to make more unsaturation, decreases L - M values and increases L + M - S values. See Figure 1.
evolution
For people to see color, the three primate cone receptors must be maximally sensitive at blue, green, and yellow-green, which requires opponency to determine colors and has color complementarity. The three cones do not have maximum sensitivity at red, green, and blue, because each sensor is then for one main color, and system has no complementary colors. Such a system has no opponency, because those opponencies have ambiguous ratios and ambiguous colors.
Photoreceptors can have the same output {univariance problem} {problem of univariance} {univariance principle} {principle of univariance} for an infinite number of stimulus frequency-intensity combinations. Different photon wavelengths have different absorption probabilities, from 0% to 10%. Higher-intensity low-probability wavelengths can make same total absorption as lower-intensity high-probability wavelengths. For example, if frequency A has probability 1% and intensity 2, and frequency B has probability 2% and intensity 1, total absorption is same.
Photon absorption causes one photoreceptor molecule to isomerize. Isomerization reactions are the same for all stimulus frequencies and intensities. Higher intensity increases number of reactions.
Color-vision systems have one or more receptor types, each able to absorb a percentage of quanta at each wavelength {wavelength mixture space}. For all receptor types, different wavelength and intensity combinations can result in same output.
Colors {colors} {color, categories} are distinguishable.
The eleven fundamental color categories are white, black, red, green, blue, orange, yellow, pink, brown, purple (violet), and gray [Byrne and Hilbert, 1997] [Wallach, 1963].
major and minor colors
Major colors are red, yellow, green, and blue. Yellow is red and green. Green is yellow and blue. Minor colors are orange, chartreuse, cyan, and magenta. Orange is red and yellow. Chartreuse is yellow and green {chartreuse, color mixture}. Cyan is green and blue {cyan, color mixture}. Magenta is red and blue. Halftones are between major and minor color categories: red-orange {vermilion, color mixture}, orange-yellow, yellow-chartreuse, chartreuse-green, green-cyan {spring green, color mixture}, cyan-blue {turquoise, color mixture}, blue-violet {indigo, color mixture} {ultramarine, color mixture}, indigo-magenta or blue-magenta {violet, color mixture}, and magenta-red {crimson, color mixture}.
white
White is relatively higher in brightness than adjacent surfaces. Adding white to color makes color lighter. However, increasing colored-light intensity does not make white.
white: intensity
When light is too dim for cones, people see whites, grays, and blacks. When light is intense enough for cones, people see whites, grays, and blacks if no color predominates.
white: complementary colors
Spectral colors have complementary colors. Color and complementary color mix to make white, gray, or black. Two spectral colors mix to make intermediate color, which has a complementary color. Mixing two spectral colors and intermediate-color complementary color makes white, gray, or black.
black
Black is relatively lower in brightness than adjacent surfaces. Black is not absence of visual sense qualities but is a color.
gray
Gray is relatively the same brightness as adjacent surfaces.
red
Red light is absence of blue and green, and so is absence of cyan, its additive complementary color. Red pigment is absence of green, its subtractive complementary color.
red: purity
Spectral red cannot be a mixture of other colors. Pigment red cannot be a mixture of other colors.
red: properties
Red is alerting color. Red is warm color, not cool color. Red is light color.
red: mixing
Red mixes with white to make pink.
Spectral red blends with spectral cyan to make white. Pigment red blends with pigment green to make black. Spectral red blends with spectral yellow to make orange. Pigment red blends with pigment yellow to make brown. Spectral red blends with spectral blue or violet to make purples. Pigment red blends with pigment blue or violet to make purples.
red: distance
People do not see red as well at farther distances.
red: retina
People do not see red as well at visual periphery.
red: range
Red has widest color range because reds have longest wavelengths and largest frequency range.
red: intensity
Red can fade in intensity to brown then black.
red: evolution
Perhaps, red evolved to discriminate food.
blue
Blue light is absence of red and green, so blue is absence of yellow, its additive complementary color. Blue pigment is absence of red and green, so blue is absence of orange, its subtractive complementary color.
blue: purity
Spectral blue cannot be a mixture of other colors. Pigment blue cannot be a mixture of other colors.
blue: properties
Blue is calming color. Blue is cool color, not warm color. Blue is light color.
blue: mixing
Blue mixes with white to make pastel blue.
Spectral blue blends with spectral yellow to make white. Pigment blue blends with pigment yellow to make black. Spectral blue blends with spectral green to make cyan. Pigment blue blends with pigment green to make dark blue-green. Spectral blue blends with spectral red to make purples. Pigment blue blends with pigment red to make purples.
blue: distance
People see blue well at farther distances.
blue: retina
People see blue well at visual periphery.
blue: range
Blue has narrow wavelength range.
blue: evolution
Perhaps, blue evolved to tell when sky is changing or to see certain objects against sky.
blue: saturation
Teal is less saturated cyan.
green
Green light is absence of red and blue, and so magenta, its additive complementary color. Green pigment is absence of red, its subtractive complementary color.
green: purity
Spectral green can mix blue and yellow. Pigment green can mix blue and yellow.
green: properties
Green is neutral color in alertness. Green is cool color. Green is light color.
green: mixing
Green mixes with white to make pastel green.
Spectral green blends with spectral magenta to make white. Pigment green blends with pigment magenta to make black. Spectral green blends with spectral orange to make yellow. Pigment green blends with pigment orange to make brown. Spectral green blends with spectral blue to make cyan. Pigment green blends with pigment blue to make dark blue-green.
green: distance
People see green OK at farther distances.
green: retina
People do not see green well at visual periphery.
green: range
Green has wide wavelength range.
green: evolution
Perhaps, green evolved to discriminate fruit and vegetable ripening.
yellow
Yellow light is absence of blue, because blue is its additive complementary color. Yellow pigment is absence of indigo or violet, its subtractive complementary color.
yellow: purity
Spectral yellow can mix red and green. Pigment yellow cannot be a mixture of other colors.
yellow: properties
Yellow is neutral color in alertness. Yellow is warm color. Yellow is light color.
yellow: mixing
Yellow mixes with white to make pastel yellow.
Spectral yellow blends with spectral blue to make white. Pigment yellow blends with pigment blue to make green. Spectral yellow blends with spectral red to make orange. Pigment yellow blends with pigment red to make brown. Olive is dark low-saturation yellow (dark yellow-green).
yellow: distance
People see yellow OK at farther distances.
yellow: retina
People do not see yellow well at visual periphery.
yellow: range
Yellow has narrow wavelength range.
orange: purity
Spectral orange can mix red and yellow. Pigment orange can mix red and yellow.
orange: properties
Orange is slightly alerting color. Orange is warm color. Orange is light color.
orange: mixing
Orange mixes with white to make pastel orange.
Spectral orange blends with spectral blue-green to make white. Pigment orange blends with pigment blue-green to make black. Spectral orange blends with spectral cyan to make yellow. Pigment orange blends with pigment cyan to make brown. Spectral orange blends with spectral red to make light red-orange. Pigment orange blends with pigment red to make dark red-orange.
orange: distance
People do not see orange well at farther distances.
orange: retina
People do not see orange well at visual periphery.
orange: range
Orange has narrow wavelength range.
violet: purity
Spectral violet can mix blue and red. Pigment violet has red and so is purple.
violet: properties
Violet is calming color. Violet is cool color. Violet is light color.
violet: mixing
Violet mixes with white to make pastel violet.
Spectral violet blends with spectral yellow-green to make white. Pigment violet blends with pigment yellow-green to make black. Spectral violet blends with spectral red to make purples. Pigment violet blends with pigment red to make purples.
violet: distance
People see violet well at farther distances.
violet: retina
People see violet well at visual periphery.
violet: range
Violet has narrow wavelength range.
violet: intensity
Violet can fade in intensity to dark purple then black.
brown: purity
Pigment brown can mix red, yellow, and green. Brown is commonest color but is not spectral color. Brown is like dark orange pigment or dark yellow-orange. Brown color depends on contrast and surface texture.
brown: properties
Brown is not alerting or calming. Brown is warm color. Brown is dark color.
brown: mixing
Brown mixes with white to make pastel brown.
Pigment brown blends with other pigments to make dark brown or black.
brown: distance
People do not see brown well at farther distances.
brown: retina
People do not see brown well at visual periphery.
brown: range
Brown is not spectral color and has no wavelength range.
purple: purity
Purples come from mixing red and blue. They have no green, to which they are complementary. Purples are non-spectral colors, because reds have longer wavelengths and blues have shorter wavelengths.
purple: saturation
Purple is low-saturation magenta.
Hue, brightness, and saturation ranges make all perceivable colors {gamut, color}. Perceivable-color range is greater than three-primary-color additive-combination range. However, allowing subtraction of red makes color gamut.
For subtractive colors, combining three pure color pigments {primary color}, such as red, yellow, and blue, can make most other colors.
secondary color
Mixing primary-color pigments {secondary color} makes magenta from red and blue, green from blue and yellow, and orange from red and yellow.
tertiary color
Mixing primary-color and secondary-color pigment {tertiary color} {intermediate color} makes chartreuse from yellow and green, cyan from blue and green, violet from blue and magenta, red-magenta, red-orange, and yellow-orange.
non-unique
Primary colors are not unique. Besides red, yellow, and blue, other triples can make most colors.
Color can have light surround and appear to reflect light {related color}. Brown and gray can appear only when other colors are present. If background is white, gray appears black. If background is black, gray appears white. Color can have dark surround and appear luminous {unrelated color}.
People can see colors {spectral color}| from illumination sources. Light from sources can have one wavelength.
seven categories
Violets are 380 to 435 nm, with middle 408 nm and range 55 nm. Blues are 435 to 500 nm, with middle 463 nm and range 65 nm. Cyans are 500 to 520 nm, with middle 510 nm and range 20 nm. Greens are 520 to 565 nm, with middle 543 nm and range 45 nm. Yellows are 565 to 590 nm, with middle 583 nm and range 35 nm. Oranges are 590 to 625 nm, with middle 608 nm and range 35 nm. Reds are 625 to 740 nm, with middle 683 nm and range 115 nm.
fifteen categories
Spectral colors start at short-wavelength purplish-blue. Purplish-blues are 400 to 450 nm, with middle 425 nm. Blues are 450 to 482 nm, with middle 465. Greenish-blues are 482 to 487 nm, with middle 485 nm. Blue-greens are 487 to 493 nm, with middle 490 nm. Bluish-greens are 493 to 498 nm, with middle 495 nm. Greens are 498 to 530 nm, with middle 510 nm. Yellowish-greens are 530 to 558 nm, with middle 550 nm. Yellow-greens are 558 to 568 nm, with middle 560 nm. Greenish-yellows are 568 to 572 nm, with middle 570 nm. Yellows are 572 to 578 nm, with middle 575 nm. Yellowish-oranges are 578 to 585, with middle 580 nm. Oranges are 585 to 595 nm, with middle 590 nm. Reddish-oranges and orange-pinks are 595 to 625 nm, with middle 610 nm. Reds and pinks are 625 to 740 nm, with middle 640 nm. Spectral colors end at long-wavelength purplish-red.
People can see colors {non-spectral hue} that have no single wavelength but require two wavelengths. For example, mixing red and blue makes magenta and other reddish purples. Such a mixture stimulates short-wavelength cones and long-wavelength cones but not middle-wavelength cones.
Blue, red, yellow, and green describe pure colors {unique hue}. Unique red occurs only at low brightness, because more brightness adds yellow. Other colors mix unique hues. For example, orange is reddish yellow or yellowish red, and purples are reddish blue or bluish red.
Three-dimensional mathematical spaces {color space} can use signals or signal combinations from the three different cone cells to give colors coordinates.
Circular color scales {color wheel} can show sequence from red to magenta.
simple additive color wheel
Colors on circle circumference can show correct color mixing. See Figure 1. Two-color mixtures have color halfway between the colors. Complementary colors are opposite. Three complementary colors are 120 degrees apart. Red is at left, blue is 120 degrees to left, and green is 120 degrees to right. Yellow is halfway between red and green. Cyan is halfway between blue and green. Magenta is halfway between red and blue. Orange is between yellow and red. Chartreuse is between yellow and green. Indigo or ultramarine is between blue and violet. Violet is between indigo or ultramarine and magenta. Non-spectral colors are in quarter-circle from violet to red. Cone color receptors, at indigo or ultramarine, green, and yellow-green positions, are in approximately half-circle.
simple subtractive color wheel
For subtractive colors, shift bluer colors one position: red opposite green, vermilion opposite cyan, orange opposite blue, yellow opposite indigo, and chartreuse opposite violet. Color subtraction makes darker colors, which are bluer, because short-wavelength receptor has higher weighting than other two receptors. It affects reds and oranges little, greens some, and blues most. Blues and greens shift toward red to add less blue, so complementary colors make black rather than blue-black. See Figure 2.
quantum chromodynamics color circle
Additive color wheel can describe quantum-chromodynamics quark color-charge complex-number vectors. On complex-plane unit circle, red coordinates are (+1, 0*i). Green coordinates are (-1/2, -(3^(0.5))*i/2). Blue coordinates are (-1/2, +(3^(0.5))*i/2). Yellow coordinates are (+1/2, -(3^(0.5))*i/2). Cyan coordinates are (-1, 0*i). Magenta coordinates are (+1/2, +(3^(0.5))*i/2).
To find color mixtures, add vectors. Two quarks add to make muons, which have no color and whose resultant vector is zero. Three quarks add to make protons and neutrons, which have no color and whose resultant vector is zero. Color mixtures that result in non-zero vectors have colors and are not physical.
color wheel by five-percent intervals
Color wheel can separate all colors equally. Divide color circle into 20 parts with 18 degrees each. Red = 0, orange = 2, yellow = 4, chartreuse = 6, green = 8, cyan = 10, blue = 12, indigo or ultramarine = 14, violet = 16, and magenta = 18. Crimson = 19, cyan-blue turquoise at 11, cyan-green at 9, yellow-orange = 3, and red-orange vermilion = 1. Primary colors are at 0, 8, and 12. Secondary colors are at 4, 10, and 18. Tertiary colors are at 2, 6, and 14/16. Complementary colors are opposite. See Figure 3.
color wheel with number line
Set magenta = 0 and green = 1. Red = 0.33, and blue = 0.33. Yellow = 0.67, and cyan = 0.67. Complementary colors add to 1.
color wheel with four points
Blue, green, yellow, and red make a square. Green is halfway between blue and yellow. Yellow is halfway between green and red. Blue is halfway between green and red in other direction. Red is halfway between yellow and blue in other direction. Complementary pigments are opposite. Adding magenta, cyan, chartreuse, and orange makes eight points, like tones of an octave but separated by equal intervals, which can be harmonic ratios: 2/1, 3/2, 4/3, and 5/4.
white and black
Color wheel has no black or white, because they mostly depend on brightness. Adding black, gray, and white makes color cylinder, on which unsaturated colors are pastels or dark colors.
Color-space systems {chromaticity diagram} {CIE Chromaticity Diagram} can use luminance Y and two coordinates, x and y, related to hue and saturation. CIE system uses spectral power distribution (SPD) of light emitted from surfaces.
tristimulus
Retina has three cone types, each with maximum-output stimulus frequency {tristimulus values}, established by eye sensitivity measurements. Using tristimulus values allows factoring out luminance brightness to establish luminance coordinate. Factoring out luminance leaves two chromaticity color coordinates.
color surface
Chromaticity coordinates define border of upside-down U-shaped color space, giving all maximum-saturation hues from 400 to 700 nm. Along the flat bottom border are purples. Plane middle regions represent decreasing saturation from edges to middle, with completely unsaturated white (because already white) in middle. For example, between middle white and border reds and purples are pinks. Central point is where x and y equal 1/3. From border to central white, regions have same color with less saturation [Hardin, 1988]. CIE system can use any three primary colors, not just red, green, and blue.
Color-space systems {Munsell color space} can use color samples spaced by equal differences. Hue is on color-circle circumference, with 100 equal hue intervals. Saturation {chroma, saturation} {chrominance} is along color-circle radius, with 10 to 18 equal intervals, for different hues. Brightness {light value} is along perpendicular above color circle, with black at 0 units and white at 10 units. Magenta is between red and violet. In Munsell system, red and cyan are on same diameter, yellow and blue are on another diameter, and green and magenta are on a diameter [Hardin, 1988].
Color-space systems {Ostwald color space} can use standard samples and depend on reflectance. Colors have three coordinates: percentage of total lumens for main wavelength C, white W, and black B. Wavelength is hue. For given wavelength, higher C gives greater purity, and higher W with lower B gives higher luminance [Hardin, 1988].
Color-space systems {Swedish Natural Color Order System} (NCS) can depend on how primary colors and other colors mix [Hardin, 1988].
If two different colors are adjacent, each color adds its complementary color to the other {color contrast}. If bright color is beside dark color, contrast increases. If white and black areas are adjacent, they add opposite color to each other. If another color overlays background color, brighter color dominates. If brighter color is in background, it shines through overlay. If darker color is in background, overlay hides it.
Two adjacent different-colored objects have enhanced color differences {successive contrast} {simultaneous contrast}.
All colors from surface point can mix {color mixture}.
intermediate color
Two colors mix to make the intermediate color. For example, red and orange make red-orange vermilion. See Figure 1.
colors mix uniquely
Colors blend with other colors differently.
additive color mixture
Colors from light sources add {additive color mixture}. No additive spectral-color mixture can make blue or red. Magenta and orange cannot make red, because magenta has blue, orange has yellow and green, and red has no blue or green. Indigo and cyan cannot make blue, because indigo has red and cyan has green, and blue has no green or red.
subtractive color mixture
Colors from pigmented surfaces have colors from source illumination minus colors absorbed by pigments {subtractive color mixture}. Colors from pigment reflections cannot add to make red or to make blue. Blue and yellow pigments reflect green, because both reflect some green, and sum of greens is more than reflected blue or yellow. Red and yellow pigments reflect orange, because each reflects some orange, and sum of oranges is more than reflected red or yellow.
For subtractive colors, mixing cannot make red, blue, or yellow. Magenta and orange cannot make red, because magenta has blue, orange has yellow and green, and red has no blue or green. Indigo and cyan cannot make blue, because indigo has red and cyan has green, and blue has no red or green. Chartreuse and orange cannot make yellow, because chartreuse has green and some indigo, orange has red and some indigo, and yellow has no indigo.
pastel colors
Colors mix with white to make pastel colors.
similarity
Similar colors mix to make the intermediate color.
primary additive colors
Red, green, and blue are the primary additive colors.
primary subtractive colors
Red, yellow, and blue, or magenta, yellow, and cyan, are the primary subtractive colors.
secondary additive colors
Primary additive-color mixtures make secondary additive colors: yellow from red and green, magenta from red and blue, and cyan from green and blue.
secondary subtractive colors
Primary subtractive-color mixtures make secondary subtractive colors: orange from red and yellow, magenta from red and blue, and green from yellow and blue.
tertiary additive colors
Mixing primary and secondary additive colors makes tertiary additive colors: orange from red and yellow, violet from blue and magenta, and chartreuse from yellow and green.
tertiary subtractive colors
Mixing primary and secondary subtractive colors makes tertiary subtractive colors: cyan from blue and green, violet from blue and magenta, and chartreuse from yellow and green.
Two colors {complementary color}| can add to make white. Complementary colors can be primary, secondary, or tertiary colors.
complementary additive colors
Colors with equal amounts of red, green, and blue make white. Red and cyan, yellow and blue, or green and magenta make white.
Equal red, blue, and green contributions make white light.
complementary subtractive colors
Colors that mix to make equal amounts of red, yellow, and blue make black. Orange and blue, yellow and indigo/violet, or green and red make black. Equal magenta, yellow, and cyan contributions make black.
Grassmann described color-mixing laws {Grassmann's laws} {Grassmann laws}. Grassmann's laws are vector additions and multiplications in wavelength mixture space.
If two pairs of wavelengths at specific intensities result in same color, adding the pairs gives same color: if C1 + C2 = x and C3 + C4 = x, then C1 + C2 + C3 + C4 = x. For example, if blue-and-yellow pair makes green, and two greens together make same green, adding pairs makes same green.
If pair of wavelengths at specific intensities makes color, adding same wavelength and intensity to each makes same color as adding it to the pair. If C1 + C2 = x and C3 = y, then (C1 + C3) + (C2 + C3) = (C1 + C2) + C3 = z. For example, if blue-and-yellow pair makes green, adding red to blue and to yellow makes same color as adding red to the pair.
If pair of wavelengths at specific intensities makes color, changing both intensities equally makes same color as changing pair intensity. If C1 + C2 = x, then n*C1 + n*C2 = n*(C1 + C2) = w. For example, if blue-and-yellow pair makes green, increasing both color intensities by same amount makes same green, only brighter.
Wheel with black and white areas, rotated five Hz to ten Hz to give flicker rate below fusion frequency, in strong light, can produce intense colors {Benham's top} {Benham top} {Benham disk}, because color results from different color-receptor-system time-constants.
Color perception depends on hue, saturation, and brightness. Mostly hue and saturation {chromaticity} make colors. Brightness does not affect chromaticity much [Kandel et al., 1991] [Thompson, 1995].
Spectral colors depend on light wavelength and frequency {hue}. People can distinguish 160 hues, from light of wavelength 400 nm to 700 nm. Therefore, people can distinguish colors differing by approximately 2 nm of wavelength.
color mixtures
Hue can come from light of one wavelength or light mixtures with different wavelengths. Hue takes the weighted average of the wavelengths. Assume colors can have brightness 0 to 100. If red is 100, green is 0, and blue is 0, hue is red at maximum brightness. If red is 50, green is 0, and blue is 0, hue is red at half maximum brightness. If red is 25, green is 0, and blue is 0, hue is red at quarter maximum brightness.
If red is 100, green is 100, and blue is 0, hue is yellow at maximum brightness. If red is 50, green is 50, and blue is 0, hue is yellow at half maximum brightness. If red is 25, green is 25, and blue is 0, hue is yellow at quarter maximum brightness.
If red is 100, green is 50, and blue is 0, hue is orange at maximum brightness. If red is 50, green is 25, and blue is 0, hue is orange at half maximum brightness. If red is 24, green is 12, and blue is 0, hue is orange at quarter maximum brightness.
Fraction of incident light transmitted or reflected diffusely {lightness} {luminance factor}. Lightness sums the three primary-color (red, green, and blue) brightnesses. Assume each color can have brightness 0 to 100. For example, if red is 100, green is 100, and blue is 100, lightness is maximum brightness. If red is 100, green is 100, and blue is 50, lightness is 83% maximum brightness. If red is 100, green is 50, and blue is 50, lightness is 67% maximum brightness. If red is 67, green is 17, and blue is 17, lightness is 33% maximum brightness. If red is 17, green is 17, and blue is 17, lightness is 17% maximum brightness.
Pure saturated color {saturation, color}| {purity, color} has no white, gray, or black. White, gray, and black have zero purity. Spectral colors can have different white, gray, or black percentages (unsaturation). Saturated pigments mixed with black make dark colors, like ochre. Saturated pigments mixed with white make light pastel colors, like pink.
frequency range
The purest most-saturated color has light with one wavelength. Saturated color pigments reflect light with narrow wavelength range. Unsaturated pigments reflect light with wide wavelength range.
colors and saturation
All spectral colors can mix with white. White is lightest and looks least saturated. Yellow is the lightest color. Monochromatic yellows have largest saturation range (as in Munsell color system), change least as saturation changes, and look least saturated (most white) at all saturation levels. Green is second-lightest color. Monochromatic greens have second-largest saturation range, change second-least as saturation changes, and look second-least saturated (second-most white) at all saturation levels. Red is third-lightest color. Monochromatic reds have average saturation range, change third-least as saturation changes, and look third-least saturated (third-most white) at all saturation levels. Blue is darkest color. Monochromatic blues have smallest saturation range, change most as saturation changes, and look fourth-least saturated (least white) at all saturation levels. Black is darkest and looks most saturated.
calculation
Whiteness, grayness, and blackness have all three primary colors (red, green, and blue) in equal amounts. Whiteness, grayness, or blackness level is brightness of lowest-level primary color times three. Subtracting the lowest level from all three primary colors and summing the two highest calculates hue brightness. Total brightness sums primary-color brightnesses. Saturation is hue brightness divided by brightness. Assume colors can have brightness 0 to 100. If red is 100, green is 100, and blue is 100, whiteness is maximum. If red is 50, green is 50, and blue is 50, grayness is half maximum. If red is 25, green is 25, and blue is 25, grayness is quarter maximum.
Assume maximum brightness is 100%. If red is 33%, green is 33%, and blue is 33%, brightness is 100% = (33% + 33% + 33%), whiteness is 100% = (33% + 33% + 33%), hue is white at 0%, and saturation is 0% = (0% / 100%). If red is 17%, green is 17%, and blue is 17%, brightness is 50% = (17% + 17% + 17%), whiteness is 50% = (17% + 17% + 17%), hue is white at 0%, and saturation is 0% = (0% / 50%). If red is 33%, green is 33%, and blue is 17%, brightness is 83% = (33% + 33% + 17%), whiteness is 50% = (17% + 17% + 17%), hue is yellow at 33% = (33% - 17%) + (33% - 17%), and saturation is 40% = (33% / 83%). If red is 67%, green is 17%, and blue is 17%, brightness is 100% = (67% + 17% + 17%), whiteness is 50% = (17% + 17% + 17%), hue is red at 50% = (67% - 17%), and saturation is 50% = (50% / 100%). If red is 100%, green is 0%, and blue is 0%, brightness is 100% = (100% + 0% + 0%), whiteness is 0% = (0% + 0% + 0%), hue is red at 100% = (100% - 0%), and saturation is 100% = (100% / 100%).
Assume colors can have brightness 0 to 100. If red is 100, green is 50, and blue is 50, red is 50 = 100 - 50, green is 0 = 50 - 50, blue is 0 = 50 - 50, brightness is 200, whiteness is 150 = 50 + 50 + 50, and hue is pink with red saturation of 25 = 50 / 200. If red is 100, green is 100, and blue is 50, red is 50 = 100 - 50, green is 50 = 100 - 50, blue is 0 = 50 - 50, brightness is 250, whiteness is 150 = 50 + 50 + 50, and hue is yellow with saturation of 40% = (50 + 50) / 100 = 100 / 250. If red is 75, green is 50, and blue is 25, red is 50 = 75 - 25, green is 25 = 50 - 25, blue is 0 = 25 - 25, brightness is 150, whiteness is 75 = 25 + 25 + 25, and hue is orange with saturation of 50% = (50 + 25) / 150 = 75 / 150.
Hue depends on saturation {Abney effect}.
If luminance is enough to stimulate cones, hue changes as luminance changes {Bezold-Brücke phenomenon} {Bezold-Brücke effect}.
At constant luminance, brightness depends on both saturation and hue {Helmholtz-Kohlrausch effect}. If hue is constant, brightness increases with saturation. If saturation is constant, brightness changes with hue.
Saturation increases as luminance increases {Hunt effect}.
Systems that can perform same visual functions that people perform can have no qualia {absent qualia}. Perhaps, machines can duplicate neuron and synapse functions, as in the China-body system [Block, 1980], and so do anything that human visual system can do. Presumably, system physical states and mechanisms, no matter how complex, do not have or need qualia. System has inputs, processes, and outputs. Perhaps, such systems can have qualia, but complexity, large scale, or inability to measure prevents people from knowing.
Perhaps, hue can be not any combination of red, blue, green, or yellow {alien color}.
Planets {Inverted Earth} {inverted qualia} can have complementary colors of Earth things [Block, 1990]. For same things, its people experience complementary color compared to Earth-people color experience. However, Inverted-Earth people call what they see complementary color names rather than Earth color names, because their vocabulary is different. When seeing tree leaves, Inverted-Earth people see magenta and say green.
If Earth people go to Inverted Earth and wear inverting-color lenses, they see same colors as on Earth and call colors same names as on Earth. When seeing tree leaves, they see green and call them green, because they use Earth language.
If Earth people go to Inverted Earth and do not wear inverting-color lenses, they see complementary colors rather than Earth colors and call them Earth names for complementary colors. However, if they stay there, they learn to use Inverted-Earth language and call complementary colors Inverted-Earth names, though phenomena remain unchanged. When seeing tree leaves, they see magenta and say green. Intentions change though objects remain the same. Therefore, phenomena are not representations.
problems
Intentions probably do not change, because situation requires no adaptations. The representation is fundamentally the same.
Perhaps, qualia do change.
Perhaps, spectrum can invert, so people see short-wavelength light as red and long-wavelength light as blue {inverted spectrum}. Perhaps, phenomena and experiences can be their opposites without affecting moods, emotions, body sensations, perceptions, cognitions, or behaviors. Subject experiences differently, but applies same functions as other people, so subject reactions and initiations are no different than normal. This can start at birth or change through learning and maturation. Perhaps, behavior and perception differences diminish over time by forgetting or adaptation.
representation and phenomena
Seemingly, for inverted spectrum, representations are the same, but inverted phenomena replace phenomena. Functions or physical states remain identical, but qualia differ. If phenomena involve representations, inverted spectra are not metaphysically possible. If phenomena do not involve representations, inverted spectra are metaphysically possible.
inversion can be impossible
Inverted spectra are not necessarily conceptually possible, because they can lead to internal contradictions. Colors do not have exact inversions, because colors mix differently, so no complete and consistent color inversion is possible.
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Date Modified: 2022.0225