in a dark room - it wont matter :P
black absorbs and heat from LIGHT ENERGY more than other colors. so yeah- its not gonna do anything either way spraying it with rad paint. I've had black intercoolers and normal ones - they worked the same.
for the record - "sleeper" was cool in 1998. just get a big scary front mount that smiles at everyone
also - window tint doesnt reflect... thats why dark tint + black leather + black car = MUST HAVE A/C