Poly bushings come in different colors to represent different durometers (hardness)
I've only seen red available for Fiero applications. If I recall the black bushings are not polyurethane but a different material with graphite lubricant embedded into them.
You cannot paint them because the paint won't adhere properly and once greased the paint will just peel off.
Be careful with the type of paint you use, Some chemicals can react with the urethane and soften it.
Also you don't want to get paint on the contact surfaces because the paint could gall and damage the bushings. Poly bushings are designed to be free-floating and anything other than a lubricant getting between the bushing and sleeve surface can cause problems.
[This message has been edited by Oreif (edited 02-14-2010).]