Psychology and it's view of vision:

The opponent-process theory was first proposed by the physiologist Edward Hering in 1878 and revised in 1957 by the researchers Leon Hurvich and Dorthea Jamison.

According to this theory, three classes of cells respond by increasing or decreasing their rate of firing when different colors are present.
The red/green cells increase their firing when red is present and decrease it when green is present.
The yellow/blue cells have an increased response to yellow and a decreased response to blue.
Another type of cell increases its response rate for white light and decreases in the absense of light.

As opposed to the trichromatic theory.