I did look at the original Rootes drawing (with Matt Olsen's help - thank you). Colour was 'hammer grey'. No more info on the drg. I think this is the paint also used on the oil filler cap, and it's close to silver Hammerite.
The eBay one is in a Chrysler packet, which means it was made after late 1969. I guess black was cheaper than 'hammer grey'. Didn't Henry Ford discover the same thing?