I'm restoring a very early QT Firebirds, and looked in to the same issue.
My machine has been subject to what they sometimes in the antique business call "enhancing", or the application of an overcoat short of full refinishing. But mine looks like it either had a lightly applied black paint or a very dark black stain originally.
I tried to find as many pictures as I could of machines in original or as-found condition (Reed slot machines has pictures like that for most of his machines, including various QTs - I think one of the ones below, is one of his).
As for colors, mine turned out to have been originally been painted yellow under the jackpot but with red painted over that, maybe even very early on. I think it may have varied as to whether they painted the sides of the jackpot the main blue color, or the bright color (yellow or red) under the jackpot, but I'm not certain about that.
- A very early model like mine, with the large coin view window and no coin return.
- An example of a later version with both the reduced-size coin view window, and probably a covered-over slot for a missing coin return.
- Mills_QT-Firebird-original-1331083436.jpg (31.39 KiB) Viewed 4693 times
Restored Mills 5c Extraordinary "barn find", long gone - now restoring 1934 5c Extraordinary Gold Award with original World's Fair reel strips
Restoring early Mills 5c Firebird (large coin view window)
About to take on a Mills 5c Vest Pocket