I don't know about colors for the inside, but I say go for mounting the PSU outside. You obviously can tackle the wiring ok, and I'm sure you can find someway to incorporate it into the "theme" when ya get one

Nothing wrong with being different. And I think the PSU not being in there, as long as you still have intake/exhaust, will help the heat problem, not hinder it. a 120mm exhaust where the PSU used to be will be more than adequate.