The DeLorean: The car itself would be counted as an artifact, not a land, and would therefore be colorless. Doc's Garage, on the other hand, would likely be blue/red, as that tends to be the typical mad scientist color combination.

Agent P's Lair: Blue sounds pretty good, with a healthy dose of white thrown in, since Perry works as part of a government organization protecting innocent people from the evil machinations of Dr. Doofenshmirtz.