Based on the "purity" of the values and lack of grey in the photo, I would say the colors are black and white. Online photos of the NS heritage unit and this Lionel link with a caboose seem to confirm that guess. How ironic -- it's possible that the "colors" are hiding in plain sight! :-}
https://www.lionel.com/product...FA3A&PageID=2119
http://trn.trains.com/sitefile...9390-3C937D2CD630%7D
Hope this helps,
Tomlinson Run Railroad
p.s. Is that a "drum head" on the railing?