[Right Wing Professor]

Neither you nor Alamo Girl evidently understand the physiology of color vision. Most of us have three color pigments, which absorb light maximally in the region of red, green and blue. Those three pigments are the reason why there are three primary colors, and why any color can to human senses be reproduced by three primary colors. But that's just to human senses; we can easily create two colors that look identical to people but are entirely different to a machine, to another organism, or even to a human being with a particular kind of mutation is a gene for one of the color pigments.

[MacDorcha]

I understand "vision" perfectly well.

It's "color" that I'm disputing.

Not the "perception of" but the "color itself"

Do keep up if you'r going to dog me.

[Alamo-Girl]

Er, I am not at all overlooking the molecular machinery of vision.

The point of a universal is that it exists - whether or not I or anyone else can perceive it is beside the point.

If one is a Nominalist then universals do not exist. There is no objective, universal "green" - it is a figment of a Normalist's imagination.