It comes black. The problem with painting it....it is VERY flexable. The first time you hit a bug with it, the paint is going to crack and come off. I have seen a few painted, but they were a custom piece that was stiff as hell. The Ford Mach 1 version is too flimsy to paint.
Anyway, leave it the natural black. Like verti sez, you're going to need more flex-agent than paint for a flimsy plastic part like that. Besides, they look great in black against any color IMHO...
If you use the Ford spoiler, you will have to do a considerable amount of stretching and pulling on it to get it installed in the proper position. I doubt a coat of paint would survive that without cracking.
Leave it black. Painting it will only chip an flake off?
But will advise to bolt it on. I used 1/4" nuts an bolts with finder washers. Didn't want to loose it somewhere on the road or freeway? To pricey to spend $ an get another.