According to the 52 and 53 GM Vehicle Information kits, the inner grille bars were painted Thistle Gray, and outer grille bars painted body color, while the bumpers were painted Anvil Gray. There was no mention of hubcap color on those. I don't know how much difference there was between Thistle Gray and Anvil Gray.
This lists Thistle Gray as Ditzler (PPG) 30873 paint code, but makes no mention of Anvil Gray.
[on edit]OK, here's a pic of a 53 3100 from back in the day. It sports Korean war era painted hubcaps and bumpers. It looks like Thistle Gray is slightly darker than Anvil Gray, but hard to tell the difference.
