The battery trays in my 63 Valiant, 65 Barracuda, 66 Barracuda, 67 Barracuda, 69 Barracuda, 64 Polara and 67 Charger were all body color originally. But these seven Mopars are by no means all that were built, and I have no factory documentation. I know what was correct for my cars (and I've owned all but one of them longer than many here have been alive), but cannot and do not claim to know whether my experience is correct for all A and B body Mopars from every assembly plant or even from a single assembly plant of that era. 100% consistent Chrysler was not.
Add to that the fact that these cars are 50-60 years old, and many parts, including battery trays, have been replaced over the years. Not always easy to tell, either.