I figure there's enough SPFs around here who can help me out...
I see lots of color photos of PRR structures where they appear to be two-tone gray with red window sashes instead of the more familiar tan/brown/red scheme. In one book I see a shot of BANKS tower in 1956 where it was freshly painted in what appears quite clearly to be two-tone gray (the rest of the colors look correct, so I doubt it's a film issue). Yet later there's a photo taken in 1967 of a very weather-beaten BANKS tower in a tan/brown combo.
So, is it a function of film age or did the PRR actually use a two-tone gray from time to time?