Silver reflects the heat so the item doesn’t absorb heat from an outside source (the sun in the case of a car) Black radiates heat that the item has absorbed so that is why it feels hot to the touch.
I think the reason the rads & coolers are left silver or plain Ali is to make it look nice, if you see original fitment stuff its generally black. The original RS500 coolers are black as are most IC i've come across.
Thats how I've always understood it.
Last edited by ECOS95; Jan 8, 2010 at 12:10 PM.