Scale has the best advise here. I would follow his instructions except I don't see the need for primer. And the original paint enough to provide a good base to paint over, feather the lines between colors. Rustolium epoxy appliance paint is a great match for Ultracote white and if left for a week prior to exposing to fuel is quite fuel resistant. It covers really well so no need to worry about getting the darker colors covered. For even better spray quality, run hot tap water over the can for about 10 min. Apply 3 light coats 5 min apart, wait 15 min and then a medium wet coat.