I saw something on this recently. I have to assume that Y chromosomes have one colour-sensing cone otherwise by this logic all men would be dichromatic? I'm a

I saw something on this recently. I have to assume that Y chromosomes have one colour-sensing cone otherwise by this logic all men would be dichromatic? I'm also struggling to understand how if one X chromosome has these two genes, having two X chromosomes (so more of the same 2 genes) would result in different colour-sensing cones. Finally, it's interesting that the identified tetrochomats cannot see things in the ultraviolet (or otherwise infrared) spectrum, only increased colour differentiation. Perhaps, they really are but the brain interprets them as related to our existing colour map, in the same way that regular trichromats identify a connection between red and violet.