The spectrum itself doesn't really care where we make divisions, as it's just a gradient in a natural system. We're the ones who make the distinctions because we can sense and perceive certain ranges. If we grant the universe a vocabulary for a moment, would it just call the whole EM spectrum by one name, as shades of one kind of energy? Does 750nm vs. 890nm make a difference to the star giving off the light? Does the light being in our visible spectrum make any difference to anyone but humans and other life forms that have similar ranges (other animals, plants, perhaps some ET from a similar planet on the far side of the galaxy)? If some other race somewhere happened to have a system that wasn't so simple and robust, perhaps they have ten cones and call each 3-nanometer range or so by a different name. We ourselves can measure infrared and ultraviolet with equipment and they are visible to different species on our planet directly. Surely those count as present in the bigger scheme of things.

Here's a philosophical question that's always made me curious: We know that the same wavelength is called the same color by most people within a cultural group. We know that a particular frequency can be assigned a standardized scientific code name and scaled to a number like a bit count reliably. However, how can we be sure that what person A and person B both call "red" actually appear as the same color to them, subjectively? They've both learned from others that a certain color is "red", but do they really see that range of wavelengths the same internally? Given the similarities of the eyes and brains, it's probably pretty close. Yet how could we know that two people with healthy eyes and healthy brains actually perceive the same wavelengths the same? What if what I call "brown" and Corion also calls "brown" look to me in my mind's eye like BrowserUk's green and looks inside Corion's head like BrowserUk's yellow? So long as the same wavelength gets processed the same over time for each of us, does it even matter if we perceive it differently?

Also interesting to me is the idea of innate extra ability to process colors. Do outstanding visual artists perhaps not process colors quite the same as other people? We know that some people have limits in color processing below the norm, and some people have a fourth cone type. Are there some people who see a great many colors with greater accuracy than the rest of us? I sure know people who can pick fabric and paint colors apart at much wider distances than a sample card and those who can barely see the differences with the swatches side by side. Is that learned by exposure and practice or is it biological? Like many things, is it some of both?