I do have a photograph of an enclosed solarium-observation car being used on the Burlington/Rio Grande/Western Pacific “Exposition Flyer” train, taken probably about 1939. However the car is painted in the standard Pullman Green, and not the Grande gold and silver that Walthers offers in their Rio Grande heavyweight cars.
I do know that some of the Rio Grande heavyweights were painted in the Grande Gold and Silver for use on the “Royal Gorge” train in the late 'forties, early 'fifties, but I have no photos of an open-end observation car ever painted in that color (though I do believe that the train carried an open-end observation car in the 'twenties and 'thirties).
I do use the Walthers enclosed Solarium-observation car on my own Grande gold and silver “proto-lance” version of the 1950 “Royal Gorge”, but frankly, I don’t think it’s prototypical. However, it looks kind of cool. [:P]
But in a lot of cases, the Walthers paint schemes on most of their ‘heavyweights’ tends to take these cars out of the ‘standard’ heavyweight era and put them in the ‘transitional’ era, when railroads were repainting older Pullman-standard cars to ‘fit in’ with the newer streamline cars they were ordering as replacements.