I've liked the ones I've seen in gun metal gray with black & silver accessories/piping/etc. Very clean looking. It was a cummins.
What color is the truck? What colors are your other parts like suspension, decals etc.?What color scheme should I paint the engine this time? Last run was rusted black and corroded aluminum with a smattering of grease and oil. (no paint)
Barny purple. Oh wait, thats been done.