The ability to perceive color.
Color vision is a function of the brain's ability to interpret the complex way in which light is reflected off every object in nature. What the human eye sees as color is not a quality of an object itself, nor a quality of the light reflected off the object; it is actually an effect of the stimulation of different parts of the brain's visual system by the varying wavelengths of light.
Each of three types of light receptors called cones, located in the retina of the eye, recognizes certain ranges of wavelengths of light as blue, green, or red. From the cones, color signals pass via neurons along the visual pathway where they are mixed and matched to create the perception of the full spectrum of 5 million colors in the world.
Because each person's neurons are unique, each of us sees color somewhat differently. Color blindness, an
inherited condition which affects more men than women, has two varieties: monochromats lack all cone receptors and cannot see any color; dichromats lack either red-green or blue-yellow cone receptors and cannot perceive hues in those respective ranges. Another phenomenon, known as color weakness or anomalous trichromat, refers to the situation where a person can perceive a given color, but needs greater intensity of the associated wavelength in order to see it normally.
See also Vision