I remember seeing (some time back, can't remember where) someone claim he could determine what color the paint on a locomotive was from a b&w image. He went into rather complicated technical explantions, which sound pretty good if you don't know anything about b&w photography.
The film, lens, filter, developer and paper are all going to combine in a unique way, even before you consider sun angle, the possibility that the cab was painted in a different year than the jacket, etc.
I've been involved in several loco repaints in the past few years, some of which left the boiler jacket untouched while the cab and tender were painted. The jacket would look "lighter" on a B&W print in this situation, but still be black.
I have no idea what colors were used on D&RGW locos, but b&w photos will neither prove nor disprove anyone's position.
JAC