White interiors of that era all had a contrasting color: black, green, blue, etc. What I'm referring to is the door treatments on the Road Runner B-bodies of the era. I believe the GTX & Sport Sat were also that way, as was a '68 Charger I owned, though it of course had the (white) padded uppers. Its headliner was white, and my '69 RR was black. So Dodge may have done white interiors differently for the Coronets.
It's best in any case to view the Trim & Color Guides on the Hamtramck Historical site if known-original cars aren't handy, and you'll see what I'm saying.