Red Passenger cars in the era of Pullman Green on the D&RGW

I was reading some of the captions for coaches and combines of the D&RGW. These captions were in the book entiteld "Rio Grande Narrow Gauge Varnish. Colorado Rail Annual #25" By Herb Danneman.

Can anyone explain why these cars ere painted red? I've come across one explanation that mentioned that these cars were for CCC trains. There must be more to it than just that. Was the lettering gold or white? Why did the railroad select the cars that they did to be painted red? Was it their condition? I'm just trying to imagine a train with a combination of red and green cars, and why this train consist would be put together. Please forward me to an old thread if this has been covered elsewhere.

What color red are we talking about? I've seen a color image of Coach 300, and it appears to be a varnished oxide red color similar to freight cars of the same era.

thanks,

Jake Johnson