It has been noted...and here's another example...where the transmission is not the same color as the engine and bell housing. According to a KF retiree with whom I spoke at a UAW luncheon several years ago who did the work, the engine block assembly including head, pan, water pump, fan pulley, generator brackets, distributor mount base, bell housing (but not the inspection pan), and transmission (but not O/D electrical components) were assembled and then the whole thing was painted. The intake was painted separately and then mated to the exhaust manifold and attached to the block after it was painted. He did not mention that some were not done this way, but then again, his job was to assemble and paint, I would guess that as engines were picked from the bank, if a transmission choice was changed, a swap occurred and colors could change. Or, perhaps your transmission was changed by a previous owner. After 60-odd years, about anything is possible.