I have a Jan 1964 that has what I think is the original ashtray, judging by the condition of the non exposed tray. For what it is worth n=1), the upholstery color is red, which matches the factory seat and carpet color it left the factory with.
Personally, I think the matching color makes aesthetic sense, although it is very easy to replace for car shows or the next owner etc, so I would suggest whatever brings you joy, go with that color!