Of all the vehicles I've had over the years I've found that white is the easiest to keep looking clean, provided you stay outta the mud and any color looks dirty after that except possibly brown. Black looks really slick as long as you keep it clean. A little bit of dust and it looks completely thrashed. Black will also get extremely hot in the summer sun, ouch!
YELLOW IS NICE!! One of my buds has his in yellow and looking just the one hfjeff mentioned above. My personal preference is metalic-blue, ahhh so pretty.
My 81 CJ7 is original brown with the yellow and orange Renegade design on the hood and sides. I don't clean it very much though, since it pretty much looks the same clean or dirty. The paint along the sides got all scratched up from the sticker weeds and tree branches in the pastures so now I'm now a firm believer in "mud protects". And it does, since I keep mud on it, the paint never gets scratched, keep in mind that I do clean the undercarrage and drivetrain however (don't want that rust). On the occasion that I do clean her for some highway driving, the paint is clean and shiny as ever with a little waxing.
Wax On, Wax Off
