Opponent Processes

Opponent process is a colour theory that states that the human visual system interprets colour information by processing signals from photoreceptor cells in an antagonistic manner.

It suggests that there are three opponent channels, each comprising of an opposing colour pair.
Red vs Green, Blue vs Yellow, Black vs White (Luminance).

Physiological basis

In the LMS Colour Space:

• The luminous opponent channel is equal to the sum of all three cone cells (plus the rod cells in some conditions)
• The red-green opponent channel is equal to the difference of the L and M cones.
• The blue-yellow opponent channel is equal to the difference of the S cone and the sum of L and M cones.