I own a black GTP...and yes...it stays dirty year 'round.....
Personally I think that Silvermist or Galaxy Silver looks best on these cars, really sets off the lines of the car.

If my gets resprayed, it's going to be silver.

Also, I love my projectors.....

took forever to aim...

bounced like hell...

look sick.
Finally aimed them and cured the bounce..
Great light output non HID.