UV's I believe can be as bright as standard cathode lights, but in some cases, this might not be true, as they tend to be a different colour to the standard lights.
A blue standard cathode will look alot different than a blue UV (Paler most likely)
But yes, anything white will glow (I believe its just white).
I in my opinion, unless you had something UV reactive, like a water coolant system, wouldn't bother getting a UV light, but since you've already done it by mistake
Things should light up blue still though, yes.
As for the overclocking question, you would permanently overclock most likely, and as far as you don't go too far, you won't damage the hardware at all (make sure you have sufficent cooling)