I stand corrected, as I do not disagree with the observations pointed out by Mr. Gaines. An example on my part, of a lack of thought before opening mouth (or typing)!
O.K. I forgot,.........please don't beat me!
But as a note, I think this instance is an anomaly and perhaps unique, and is an example of a "quick-fix" that perhaps wasn't "sighed off" on by everyone who would have been involved in the decision making process if coloration of the exposed drum surfaces had been intend in the original engineering endeavour. As I believe has been suggested (I don't know, I wasn't there), the application of paint out of a bucket(?) with what appears to have been an oversized paint brush, sloped on inconsistently in coverage or density seems lacking in what one would anticipate in an efficient assembly line process. I wonder even if so, perhaps there were instructions of what was to be covered and what was not, and although if so, a failure of execution existed, a situation salvaged perhaps by mounting the wheel knowingly before the paint was permitted to dry thoroughly, and therefore readily displaced upon torquing?
But it still holds true and proper, I should have said: one "should not" paint these surfaces for the reasons stated, and Ford Motor Company (and others) most often practiced such with rare exception, but perhaps for "correctness" in this instance, just be sure to bolt your wheels on before the paint dries!
Scott.