Color

Color (or colour in Commonwealth English; see spelling differences) is the visual perception based on the electromagnetic spectrum.

For most humans, colors are perceived in the visible light spectrum with three types of cone cells (trichromacy).

Animal perception of color originates from different light wavelength or spectral sensitivity in cone cell types, which is then processed by the brain.

This effect can be visualized by comparing the light sources' spectral power distributions and the resulting colors.

(Schopenhauer) In 1801 Thomas Young proposed his trichromatic theory, based on the observation that any color could be matched with a combination of three lights.

Young's theory of color sensations, like so much else that this marvelous investigator achieved in advance of his time, remained unnoticed until Maxwell directed attention to it.

For each location in the visual field, the three types of cones yield three signals based on the extent to which each is stimulated.

In normal situations, when light is bright enough to strongly stimulate the cones, rods play virtually no role in vision at all.

These effects, combined, are summarized also in the Kruithof curve, which describes the change of color perception and pleasingness of light as a function of temperature and intensity.

Most forms of color blindness derive from one or more of the three classes of cone cells either being missing, having a shifted spectral sensitivity or having lower responsiveness to incoming light.

In addition, cerebral achromatopsia is caused by neural anomalies in those parts of the brain where visual processing takes place.

Individuals with the strongest form of this condition (dichromacy) will experience blue and purple, green and yellow, teal, and gray as colors of confusion, i.e.

Some invertebrates, such as the mantis shrimp, have an even higher number of cones (12) that could lead to a richer color gamut than even imaginable by humans.

[28] The philosopher Pythagoras experienced synesthesia and provided one of the first written accounts of the condition in approximately 550 BCE.

This effect is responsible for the phenomenon of afterimages, in which the eye may continue to see a bright figure after looking away from it, but in a complementary color.

[33] In reality, the visual system is constantly adapting to changes in the environment and compares the various colors in a scene to reduce the effects of the illumination.

[34][35] Both phenomena are readily explained and mathematically modeled with modern theories of chromatic adaptation and color appearance (e.g. CIECAM02, iCAM).

[36] There is no need to dismiss the trichromatic theory of vision, but rather it can be enhanced with an understanding of how the visual system adapts to changes in the viewing environment.

Without pigments or dye, fabric fibers, paint base and paper are usually made of particles that scatter white light (all colors) well in all directions.

The subtractive model also predicts the color resulting from a mixture of paints, or similar medium such as fabric dye, whether applied in layers or mixed together prior to application.

If the microstructures are spaced randomly, light of shorter wavelengths will be scattered preferentially to produce Tyndall effect colors: the blue of the sky (Rayleigh scattering, caused by structures much smaller than the wavelength of light, in this case, air molecules), the luster of opals, and the blue of human irises.

Variations in the pattern's spacing often give rise to an iridescent effect, as seen in peacock feathers, soap bubbles, films of oil, and mother of pearl, because the reflected color depends upon the viewing angle.

Numerous scientists have carried out research in butterfly wings and beetle shells, including Isaac Newton and Robert Hooke.

If it is expanded even more, it will cover more wavelengths than the yellow semichrome does, approaching white, until it is reached when the full spectrum is reflected.

They were called semichromes or full colors by the German chemist and philosopher Wilhelm Ostwald in the early 20th century.

The meanings and associations of colors can play a major role in works of art, including literature.

For example, researchers at the University of Linz in Austria demonstrated that the color red significantly decreases cognitive functioning in men.

[48] The combination of the colors red and yellow together can induce hunger, which has been capitalized on by a number of chain restaurants.

Colors vary in several different ways, including hue (shades of red, orange, yellow, green, blue, and violet, etc.

Sonoluminescence is a blue-purple created by the energy of sound waves from tiny bubbles in extreme experimental conditions, and was discovered in 1934.

Colored pencils
gray fading to rainbow colors (red to violet), then fade back to gray
The visible spectrum perceived from 390 to 710 nm wavelength
The upper disk and the lower disk have exactly the same objective color, and are in identical gray surroundings; based on context differences, humans perceive the squares as having different reflectances, and may interpret the colors as different color categories; see checker shadow illusion
Normalized typical human cone cell responses ( S , M , and L types ) to monochromatic spectral stimuli
The visual dorsal stream (green) and ventral stream (purple) are shown; the ventral stream is responsible for color perception
The CIE 1931 color space xy chromaticity diagram with the visual locus plotted using the CIE (2006) physiologically relevant LMS fundamental color matching functions transformed into the CIE 1931 xy color space and converted into Adobe RGB ; the triangle shows the gamut of Adobe RGB, the Planckian locus is shown with color temperatures labeled in Kelvins , the outer curved boundary is the spectral (or monochromatic) locus, with wavelengths shown in nanometers, the colors in this file are being specified using Adobe RGB, areas outside the triangle cannot be accurately rendered since they are outside the gamut of Adobe RGB, therefore they have been interpreted, the colors depicted depend on the gamut and color accuracy of your display
Additive color mixing: combining red and green yields yellow; combining all three primary colors together yields white
Subtractive color mixing: combining yellow and magenta yields red; combining all three primary colors together yields black
Twelve main pigment colors
Reflectance spectrum of a color-optimal reflective material. There is no known material with these properties, they are, for what we know, only theoretical. [ 44 ]
Optimal color solid or Rösch–MacAdam color solid (with D65 white point ) plotted within CIE 1931 XYZ color space . Notice the central symmetry of the solid, and the two sharp edges, one with warm colors and the other one with cold colors.
Optimal color solid plotted within the CIE L* u* v* color space , with D65 white point . Notice that it has two sharp edges, one with warm colors, and the other one with cold colors.
MacAdam limits for illuminant CIE F4 in CIE xyY
Slice of the Munsell color space in the hues of 5PB and 5Y. The point farthest from the achromatic axis in each of these two hue slices is the maximum chroma color, semichrome, or full color of that hue