Horrible idea. Your CPU will get up to as much as 80C, and you want to apply something that is Extremely Flammable? Why? Spray cans contain solvents which are very flammable. (Believe me, I've seen many lab fires.) Even after the application surface has dried I think your causing a potential fire.
Even IF you get the spray to be fire retardant - there's no point in trying to make a white wall black if it wasn't made to look like that in an interior. IOW - the Hyper will take a major performance hit. The paint will clog up in the tightly spaced area of the cooler and kill the fantastic temps thas made the cooler so popular.
If you want black - get the Xigmatek Dark Knight II, Megahelms dark shadow, Corsair A(something)that comes in black.
@ amuffin - , now now there! we all needs some loving time with the rig