<P> Two complementary theories of color vision are the trichromatic theory and the opponent process theory . The trichromatic theory , or Young -- Helmholtz theory , proposed in the 19th century by Thomas Young and Hermann von Helmholtz , as mentioned above , states that the retina 's three types of cones are preferentially sensitive to blue , green , and red . Ewald Hering proposed the opponent process theory in 1872 . It states that the visual system interprets color in an antagonistic way : red vs. green , blue vs. yellow , black vs. white . Both theories are now accepted as valid , describing different stages in visual physiology , visualized in the diagram on the right . Green ← → Magenta and Blue ← → Yellow are scales with mutually exclusive boundaries . In the same way that there can not exist a `` slightly negative '' positive number , a single eye can not perceive a bluish - yellow or a reddish - green . ( But such impossible colors can be perceived due to binocular rivalry . ) </P>
who proposed that the eye must have receptors for three colors of light
Thomas Young and Hermann von Helmholtz