The idea isn't really original, it came from a movie called "Our Idiot Brother". Here is a link to the scene that inspired it all.
00:49:13 - Oh, sweet! - Really?
00:49:16 Sweet? You'd be psyched to go to some rock club?
00:49:20 See a band called, like, Paint Store...
00:49:24 - ...or something? - Not really.
00:49:26 No, you don't.
So there you have it, the reason we are named Paint Store. Partly because it is available, partly because it is relatively sweet, and partly because it is funny. I should also mention that we are pretty much a metal band, but in many ways heavy metal culture is a bit too serious for my taste, therefore I'm down with a less serious name-vibe.