Hering's opponent colour channels do not exist in the primate retinogeniculate pathway.

We have used pure hue contrast stimuli to examine the responses of single primate retinal ganglion cells. Only one subset of these cells, those excited by the short wave sensitive cones and inhibited by the other cones, i.e. the blue-on/yellow-off variety, can distinguish white/yellow contrast. This implies that the paired opponent channels of Hering 's colour vision theory do not exist in the retinogeniculate pathway.