Actually painting the fins any color could interfer with the ability to transfer heat. Depending upon the chemical composition of the paint, the paint could act as an insulation thereby decreasing heat transfer. Besides, simply painting the heat sink black would not make the fan anymore silent (for most all paints) it would only make it black; a more efficient mechanism for heat transfer requiring a lower airflow would lower the noise created.Where are the Black Fins. As we all know the simple act of painting fins black increases the thermal dissipation rate in low light environments. If I wanted to make a heat sink more silent I would start by painting it black.