Lon,
I would guess it depends on which cars you're talking about. The very few pictures I've seen of outfit cars and such, they appear to be boxcar red, the same color just about everything on the railroad was painted. The surviving outfit cars in Baker and up Griffin Gulch are red, though it could just be the layer of paint they've weathered down to. I'll do some research and get a list from the 1947 roster up.
Talk to You Soon, Taylor