I was taking some new pics of myStang tonight and I noticedhow the radiator stands out really bad behindeverything and looks really dull. I was wondering if it would hurt anything to paint it black with some high temp paint?

 

 

go for it

 

You'd have to pull it out of the car & power wash it first to get it good so the paint would stick. I wonder if the layer of paint would affect the cooling ability of the rad at all? Just a bit??

 

You can paint the radiator butI would go to a professional paint store (the ones that the body shops use) and get their advice.There are etching cleaners that clean the metal and allow the paint to stick without having to sand the inside of each individual cooling fin.Since you would only use a very light coat of paint this would be very important since light coats are much more likely to just flake off.
If this isn't for you,go to a radiator shop and ask what they use.