Looking further in books, I have now turned up the captions that coach 300 being pictured freshly out shopped in Alamosa in red paint 7/7/40 and across the page an interior picture of 300 on 7/24/40 in Gunnision on the tail end of the Shavano, behind the parlor car.
Other pictures and captions indicate the cars are in storage in both Salida and Alamosa. I can't seem to make heads or tails to this practice with red paint. Was it cheaper than green?