Much of the GN heavyweight equipment was repainted to the orange/green "Empire Builder" scheme. Examples abound of baggage cars, RPOs, coaches, diners and solarium/observation cars in EB colors. Some baggage cars even made it to Big Sky Blue eventually.
Such re-painted cars, however, never operated behind GN steam. GN passenger trains were completely dieselized by 1951. The S-2 Northerns handled freight after that, until they were retired. Repainting of the heavyweight cars generally started after 1951, when some of them were needed for service on the Western Star and secondary trains.
There is lots of photos and films of pullman green heavyweight cars behind orange and green E7 or F3 diesels, but none I have ever found of orange/green cars behind GN steam. (The Portland section of the streamlined Empire Builder in 1947-48 occasionally was pulled by SP&S steam power.)