Dang, I had not thought about checking the maintenance manual. Stupid me...
In any case it's interesting that the paragraph you mention requires priming alclad panels (which should be already corrosion resistent due to their cladding) and no mention is made about magnesium parts, which should be even more susceptible to corrosion than all of the aluminium parts.
In any case I managed to find a few wartime color photos where it's (kinda sorta) possible to see the the color of these areas, and indeed a yellow color seems to be there.
So I'd say that the question is answered
Andrea