Wow, don't think I could see my rub rail on my Challenger, any other color. What color are you thinking about? Even with my after market graphics, the rub rail is still purple. I've not considered it, maybe I should play with the color a bit.
Being plastic or vinyl, it is so hard to find something that would stick to it, and not come off, either by a bump to a dock, or over years exposed to UV rays. The rub rails are cast in the color we get them, so if you paint or stain over them, its only surface and would only be temporary.