General purpose Navy vehicles were painted gloss gray with black lettering, as Air Force vehicles were a gloss dark blue with gold lettering (when the AF became a seperate entity) and Army a gloss olive green with white lettering. I think the USMC vehicles were just like Army vehicles but had gold lettering if I remember correctly. I am talking about their vehicles such as sedans, pickup trucks, utility vehicles and the like. Even the ambulances were painted this way. Field use units are a whole different story. In the early 80s, the Navy and Marines went to all white vehicles (they were leased from contractors) and now they take them in what ever color they arrive in from the supplier.
I am pretty sure that this is the case but I have been known to be completely wrong in the past.