If anyone's installing an IC for the way it looks, they're already missing the point. Some things are just better off left un-touched. If the IC is already too big to heat-soak, paint won't hurt it. If it does heat-soak, then paint will hurt it. It's difficult to measure where the point is that paint would affect its performance from the driver's seat, but all paints will add an insulating layer, therefore, all paints will affect aluminum's thermal transfer properties (Chemistry 101).

Anodizing can actually improve Aluminum's thermal transfer characteristics because it actually will increase the molecular surface area of the aluminum through oxidation and make the aluminum more porous. But, just like with paint, I also doubt that one would be easy to measure...

Wear your blingin' IC with pride. You're boosted for cryin' out loud. You won't fool anyone when you shift and your BOV goes "PSSSSSSSSSSSHHHHHHHHHHT"