From what I've seen and read (and some real radios I've had the pleasure to see, touch, etc.):
The radios were manufactured by various companies and subcontractors and did have some different face and case colors - though those presented in the pictures ref'd and given in this thread are perfectly typical examples. Telefunken, Torn, West and AEG all used somewhat different finishes. In addition to these standardized radio-sets, there were servo-motors, power-supplies, junction boxes, and loud-speakers - all of which could be these same colors or other OEM finishes - among them dark green, satin black, and "field gray".
The frame-racks typically seen in vehicles were also mostly standard OEM stuff supplied by different companies (of course!

). These were generally supplied to vehicle-assembly plants by the OEM wearing the prevailing base-coat color of the era - i.e., earlier war and pre-war they were a dunkelgrau-type color (in a satin or apparently even semi-glossy enamel finish, as seen in some interior photos), and in later years, the dunkelgelb-type color. So, there was usually a color-distinction between frame members and contained radios.
Best of my knowledge, these frames / racks were installed into already-finished AFV, and were not repainted to be the prevailing interior elfinbein (in closed hulls) (the same racks were used in open-top vehicles, where they would already match the exterior base-coat, which was also the open, visible interior base-coat).
So... A guy building a 222 or 223 "closed" car would comfortably use the same rack color and radio color(s) as one building a Marder or a 251.
Hope this helps!
Bob