An afterthought. If you model late 40s, early 50s, interesting livery variations apply. While your loco would need to be dipped into a pot of grey paint, with only the buffer beams being picked out in scarlet / red, the carriages could include some older wooden ones still in faded and weathered GSR maroon livery. This faded to a reddish brown colour when combined with brake dust. Pristine maroon was gone by this stage.
Pre 1955, all CIE coaches were the darker green, including the Bredins and the 1950/51 built CIE stock, which was to much the same pattern.
Needless to say, in the scenarios painted in all 3 posts above, all wagons are all-over grey. No black, no brown! And goods brakes were ten years away from getting the yellow / black wasp stripes on the duckets.