Opponent-Process Theory

An alternative proposal to the three-color theory by Karl Ewald Konstantin Hering, who suggested that three separate chemical processes occur in the retina, where the color pairs Blue-Yellow, Red-Green, and Black-White strive for balance.
The opponent-process theory states that color perception is based on three antagonistic mechanisms: Red-Green, Blue-Yellow, and Black-White. These mechanisms explain why certain colors cannot be perceived simultaneously and phenomena such as afterimages occur.