Knowing the colors of objects is not enough to helps us to recognize them.

Human beings only have 3 types of cones that receive information about color: red, green, and blue.

Opponent-Process Theory is based on the idea that the light of a particular wave length stimulates the three different receptor mechanisms, each with different spectral sensitivities.

Color deficiencies are usually explained by Opponent-Process Theory.

Color blindness is a fairly common condition and mostly seen in women.