I am just tired of red. However I am pretty sure that the mouse is attuned to the specific wavelength of light given by a red LED. Is this true? Or can I just switch one with another?
Maybe white?
That’d be purdy 
If it’s possible (and cheap enough) I’d imagine they’d already be doing it (or will be soon). I’d guarantee those would fly off the shelf. Kinda like cell phone faces.
Apparently it is possible - here’s a (rather old) article explaining how to do it. At your own risk, of course.
They’re already on the market - just kinda hard to find, apparently. Here is a review of a mouse with a blue LED. And here is a company selling a mouse that I simply must have. 24 LED colors selectable by a button on the mouse. You can also set it to scroll through all the colors while the mouse is idle.
That mouse does not use those LED - at least the ad doesn’t say it uses any of those 24 colours - those are merely there for the novelty.
Replacing the LED that’s actually being used by the tracking element in the mouse may actually cause it to stop working. Since the dectector in a red-LED mouse is designed to receive mainly red light, replacing the red LED with a blue one would result in the detector receiving much less usable signal, and your mouse would become less responsive or even inert.
This isn’t to say that it won’t work, but it probably will make your mouse more prone to error – especially with blue. Green, being closer to red than blue, should be less prone to problems.