Our observance of color is an extremely sensitive observance of a small part of the electromagnetic spectrum. Strangely, all the other wavelengths in the spectrum are foreign to us and operate on what seems like a whole different system in practice, a system of dull and repetitive as opposed to vibrant, dynamic signals. But, it is our nervous systems which have transformed light into something more than predictable waves by tuning our receivers to pick up and elaborate on each exact visible light wave.
The course of our class lecture and discussion has pointed to the conjecture that to our nervous systems, color is as constructed a perception as solid space, with our sensitivity to color depending only on three special molecules that were randomly selected for to be held in special regions of our eyes. It saddens me somewhat to think that color, which we previously thought to be so inherent to each object and living thing, is as fragile as those tiny molecules in our eyes or does not even exist. Color is really more like an abstract idea than a physical property. We rely heavily on color in our lives (for example to tell us if a food is alright to eat), but in class we see how easily our eyes can trick us into believing that objects have properties of color and solidness that they do not. We find beauty in color, yet it was created somewhere between our eye and I-function, and not by light and an object. Color shows us yet another example of how our nervous system has specialized itself to filter and obscure inputs so that our mind senses and acts in a sort of a parallel world to that which is outside the nervous system.
I'm not sure the molecules are so randomly selected (remember natural selection is operating); after all, they do, as you say, help us to detect differences between things which are important to us. Yes, color is an abstract idea, but is that really a source of sadness? One might make an argument that "reality" (assuming its out there) is generally dull and repetitive, and that it is one of the excitements/glories of the nervous system that it gives it "color", no? PG