Physical primary colors

Refers to the colors perceived by the three types of cones, which are sensory cells of the retina in the eyes of vertebrate animals. Each type of cone contains a distinctive type of pigment: one cone absorbs red light, another absorbs green, and the third type blue-violet light. Emitted or reflected/absorbed light of a given color stimulates all three types of receptors with varying effectiveness, and the pattern of these responses determines which color is perceived by the brain, which in turn recognizes four psychological primary colors (blue, yellow, red, and green).