My RHD had both remote servo hydraulic valves painted blue, small traces of the painted just showed beneath the dirt and corrosion. The canister for the vacuum pistons were silver on both. Probably zinc or a similar plating.
I truely believe that they were original when I removed and rebuilt them.
The master cylinder that is attached to the brake pedal was difficult to access the original colour, it is now black.
The clutch cylinder again was difficult to access, the replacement was silver, again zinc played or something similar.
Best wishes
Charles