"Whoever invents or discovers any new and useful process, machine, manufacture, or composition of matter, or any new and useful improvement thereof, may obtain a patent therefor, subject to the conditions and requirements of this title."
You misunderstand it. All of those things listed are "subject to the conditions and requirements of this title." The next few sections are about conditions and requirements. That's the important part.
...none of which would seem to apply. What's the prior art? It's defiantly non-obvious or someone would have done it decades ago - color screens have been around for a long time.
If you were thinking of something else, I kindly ask you to make a point, instead of asking me to prove a negative.
Color screens have been around a long time, but staring at them all day has only recently become common behavior. And the solution to a problem can be obvious even if the existence of the problem isn't obvious.
