You shouldn't paint fenders because the paint just doesn't stay looking good. My cousin is a dumbass and paints his all the time, every time you brush up against a tree or any kind of debris along the trail the paint gets torn off, or if you even get roosed bad, or hit the fender with your foot when getting on it can tear the paint off. It doesn't matter if you get paint with a flex agent in it, these plastics are very flexible and waxy, and the paint won't stick to them right. If you did paint them you'd have to be super careful the entire time you ride so you don't tear the paint up, and it would be dumb to modify your riding style because you painted your fenders. Just sell the fenders on ebay and buy a set of ones in a color you like. It'll save you money in the long run, as opposed to spending 30 bucks on paint plus hours of labor a few times a year.
