I posted this on the MR forum and got some help so I thought I’d try here too.
I model a number of different RRs and am in the process of installing working markers on my cabooses(cabeese?). Most RRs had markers showing red to the rear and green to the sides and front. A few (Santa Fe, Pennsy, N&W and, maybe Rio Grande) had red to the rear and yellow to the sides and front. Does anybody out there know for sure about the Rio Grande or any other RRs that used yellow instead of gree?
I’m talking here about the markers on the rear of the train, not the class lights on the front of the engine.
If it helps any Frisco used Adlake marker lights. They were red to the rear and green to the side.
If you do a search on Adlake you will find some and their history.