So.....if you watch one of the making of documentaries, there is a bit with John Evans. You can see the cars in the background in the process of being built. The wheels are the original bright chrome as they would have come from the manufacturer. They were obviously painted before filming. I mentioned before that they to my eyeballs they have always looked like a gunmetal color or a charcoal-ish gray. A darker color, not black.
Also, I think (not 100% sure) that this picture below is the original filming model for the Axis Chemicals scenes. I could be wrong. Maybe this was just a studio scale replica that was made. Or maybe it's the real thing but the wheels were re painted or restored for some reason. Anyway, the wheels on this are very dark and they closely matches the photos of the full size car that I posted previously.
Another thing about the the full size cars. It's not just the lighting you have to be aware of on set. Even when they aren't at their full level of shine, they will reflect a little bit of color from the objects, buildings, and various junk that is opposite of them.
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