Tangerine Scream, just to annoy all those ST owners that paid the extra $495 :)
Seriously, it's about as personal preference of a question as you can get. What colors do you like? Since we're talking aftermarket, you can go for literally anything you want. They're all going to show dirt, though some are worse than others, and they're all going to get hot.
I liked the Carbon Steel VW has for the GTI, a bit darker than Ford's current Sterling Grey Metallic. Most cars look good in black, IMO, but I like a deep, glossy finish, rather than the metallic blacks Ford's using this year. Not at all good in the keep-clean category, though. Awful lot of neutral (black/grey/silver/white) cars on the road these days, so maybe it's time to go for some color. Don't see a lot of British Racing Green these days; that would be unusual, if that's what you're looking for.