Color or colour (see spelling differences) is the visual
perceptual property corresponding in humans to the categories called red, blue,
yellow, green and others. Color derives from the spectrum of light
(distribution of light power versus wavelength) interacting in the eye with the
spectral sensitivities of the light receptors. Color categories and physical
specifications of color are also associated with objects, materials, light
sources, etc., based on their physical properties such as light absorption,
reflection, or emission spectra. By defining a color space, colors can be
identified numerically by their coordinates.
Because perception of color stems from the varying spectral
sensitivity of different types of cone cells in the retina to different parts
of the spectrum, colors may be defined and quantified by the degree to which
they stimulate these cells. These physical or physiological quantifications of
color, however, do not fully explain the psychophysical perception of color
appearance.
The science of color is sometimes called chromatics,
chromatography, colorimetry, or simply color science. It includes the
perception of color by the human eye and brain, the origin of color in
materials, color theory in art, and the physics of electromagnetic radiation in
the visible range (that is, what we commonly refer to simply as light).
