Pete, TruColor TCP-204 Western Pacific freight car red is a near match for the factory Roundhouse car color which is indeed a neat rendition if you browse through the Jim Eager WP book and study the <1950 box cars. I've studied several paints and came to the conclusion that TCP-204 was the right one for me. I now use it on all my WP cars. You could mix it with some grey to archieve a more faded result for older cars. Or fade it afterwards with a light grey filter.
There was an article on modifying this Roundhouse car in the July 1995 Mainline Modeler.
In 1950 there were 3 types of outside braced 50' WP Pullman-built cars:
12001-12150 with 12' doors and lumber door
19201-19250 with 15' doors and lumber door (taken from batch above)
40001-40100 with 12' doors and steel doors at end
Microscale makes a decal set for this car. However, the shield is not very sharp. Try to score a Champ set, which has a very clear and sharp shield.
If you follow the link Eric and Garth already published here, you'll find a rebuild I did last year of a WP 15' door car.