Thanks for the reference, I hadn't seen it previously. In males, the variation appeared to be more toward decreased color perception, except for one variation

Thanks for the reference, I hadn't seen it previously. In males, the variation appeared to be more toward decreased color perception, except for one variation associated with increased red sensitivity. It does raise the interesting but perhaps unanswerable question of the similarity or difference of the effect of the molecular variation vs. tetrachromacy on color perception. Would greater red sensitivity of L cones in effect produce equivalent visual experience as having a fourth type of cone? Since the visual system computes color on the basis of differential response in M and L cones at time t, having a greater separation of M and L spectra would be sufficient information to compute a larger range of intermediate colors vs. the normal L-M difference. The presence of another node L' between L and M could just be redundant input and not necessarily adding information to the color computation. A question that arises here is if S M L L' females have better color perception is it because of having L and L' or would it reflect L' being more distant from M than the typical single L of female trichromats. That may be significant in light of lack of clear findings of direct benefit to female color perception in those having L L' retinal mosaics. EDIT: Actually, to my way of thinking, the issue is more precisely color discrimination, which is fairly directly measurable vs color perception, a less tractable concept.