The Neural Control of Vision
H. The Function of the Midget and Parasol Channels in Vision

The upper part of Figure 32 shows how color vision is tested. One of the targets is of a different color than the other in this discrimination task. The graph below shows a monkey's performance when the animal had to discriminate a red, blue or green stimulus from white ones. The monkey does well at intact and magnocellular lesion sites (MLGN), but cannot discriminate colors at the parvocellular lesion site (PLGN).