I agree the raised ridges of the radio speaker panel were painted a lighter shade of brown and the recessed areas were painted a darker shade (like Fonz8261’s pictures). At least that’s the way it was painted on the 1952 truck we had back in the day.
You may be remembering incorrectly on the '52. The two tone interior scheme for the speaker grille & glovebox was phased out mid '51, and GM went with a single color on them per the GM notice that Tim posted.
I always thought my dad's GMC shop truck was a '48, but finally came up with a picture of it, and discovered it was a '51. I do remember that it had wing windows, though. Just shows that as we age, memories change.
