Check
this page from Tim's site, which is a page from the Chevrolet Service News that shows the '50-'53 interior paint specs.
In the '47 Engineering Features book, the base interior color was referred to as a silver gray. Exactly which gray that was (and its exact name) is unclear, but all painted interior bits were the same color (including the steering column, wheel, and horn button), except the raised ribs of the speaker grille, ash tray, and glove box door, which were a slightly lighter shade of the silver gray. That assumes that what was published is what was actually done.
I found a '49 Dupont paint chart that lists three different interior colors--Gray, Metal Gray Met., and Sheen Gray Met., but no mention of which was used where. That CSN page seems to suggest that maybe there was a change in '50, though there is no mention in the '48-'53 Engineering Features books of any interior color changes for the trucks (excluding panels and 'burbs).
At any rate, Jim's correct interior paint scheme would depend on whether his truck is an early or late '51, and exactly when the division between early and late was.
