The answer is an opponent-process theory of color vision, it was first discovered by the psychologist Ewald Hering in the year 1878. This controlled by the 3 receptors namely the blue-yellow complex, the black-white complex, and the red-green complex.
On this theory, the cells can be seen only if there is at least one color that is present. The opponent cells can not detect two colors like the greenish-re.
