How the Body Works: Color Vision

Color vision is a synthesis of red, green, and blue light which is brought about by changes in pigments within the cone cells of the retina. The human eye can recognize hundreds of different colors, which are combinations of these three colors. It is believed that three specialized types of cones exist-one responding to red light, one to green, and one to blue light. Some of these cones, however, can be stimulated by the whole visual spectrum. The variable stimulation of all the cones can register all of the colors known to man. Absence of, or defects in, the cones that respond to red, blue or green light, causes various types of color blindness. Color-blind people may not be able to see green and red, blue and yellow (although blindness to blue is rare), or any color at all, with everything appearing gray.