Renowned researchers, Thomas young and Hermann von Helmholtz, contributed to the trichromatic or three color theory of color vision. According to young, we see color because of the actions of three different receptors.
Helmholtz explained that all three types of receptors reacted to all colors, but in varying degrees, and that it was the total ‘sensation’ received by the brain that determined the colors actually seen.
Another theory was put forward by Ewald Herineg . He theorized that the retina’s receptors are mere absorbers of light, and that color discrimination begins in the coding mechanisms located further along the topic system. Instead of color being comprised of three basic colors, he suggested humans perceive color based on six primary colors. This theory is widely accepted today.