I am not certain about the models prior to 74. But, certainly by then, the bar controls and master cylinder were black anodized and semi-satin finish. The indented lettering was painted red-going-orange color.
The anodize is a tinted oxide of the parent aluminum. The sun bleaches the tint to a grey color over time. And, there may be some sublimation of the oxide that also thins the coating to allow the base aluminum color to show through the aluminum oxide which, in its pure state, is transparent.
The part can be re-anodized in nearly any color you'd like by shops that perform anodizing.
The original color ought to be observed inside the bar controls, the part where the sun don't shine, as the anodizing process occurs over the entire surface of the piece. However, this internal surface is unlikely to have been polished before anodizing. And, the showing surfaces most likely were.
Cheers,
