I'm curious about the preference for black anodizing. The heat is conducted into the fins from the transistor (or whatever the hot device is) and the fins, having a lot of surface area, conduct heat into the air in contact with them. The air then convects the heat away from the fins (assuming there is enough airflow around the fins to allow that). You can augment the convection with a fan, as well.
With heat moving by conduction and convection, the color of the heatsink wouldn't play a role. Radiative heat exchange into the heatsink might be helped by a black surface, but radiative exchange makes a negligible contribution to the process.
