When I still had my 335i (alpine white), I parked my IS (ultra white) next to it and was amazed how much brighter the IS was. It made the bmw look yellowish in comparison. I had no idea the difference would be so drastic in white paints, but it is. And I personally think the hardest paint color to keep clean is black.

 

Same here, when I put my Peal White 370Z and my Starfire Pearl 3IS next to each other, the 3IS looks a little more brighter, with the Z looking more velvet white color (hope that makes sense).

 

Yea dirt shows on black easily, but once you clean it....daaaayymmm...also the Starfire Pearl color on the IS looks yellow if parked next to the Ultra White color