I don’t know about car colors but birds can definitely be aware of their excretory process and are quite capable of aiming.
Years ago while on holiday at my best friend’s house in Maine we rowed out to Mark Island to look around. It turned out that we were there just in time for the seagull nesting season and they were none too happy to see a couple of large mammals wandering around their nursery. On noticing this we were careful to give the nests a wide berth as we walked around the island. The gulls for their part made sure to reinforce our circumspect behavior with continuous strafing runs until we got back on the boat. Curiously they consistently dropped their loads very near us on the rocks not hitting us once during the entire visit.