As seen in the little Monero clip I posted the Rio Grande ran the Yellow cars in the late 50's through the 60's Alamosa to Durango, then kept them for the Silverton Train. To me they are authentic to the Rio Grande if history is what you are after. I guess technically the red, green and yellow would be historical to the C&TS. I think the red was chosen to replace the drab looking green which did not weather well, and because the red was brighter, and perhaps did not want to be confused with the D&S by using the Grande Gold. I think the current color is nice looking although as I said I might have gone with the Grande Gold. If someone confused the C&TS Train with the D&S, maybe thats a good thing. I think the current Red overall looks more appealing than the green however. Just my opinion.
Greg