What paint?

When you paint a rad is there a special paint that i should be useing? and will it affect heat transfer after its been painted?

In an "Automotive" application, Rads are painted black to help
disipate the heat. Believe it or not.

My Swiftech rad is black, from them too.

I personally have found no difference.

awesome, so just use some normal black enamal paint?

Actually, paint adds another resistance for heat to flow out. In a water-cooling application radiation mode of heat transfer is so small it's negligible. It's actually less than one half degree. Not unless you just want it to be nice looking for like a case window.