Simon,
This won't help much, because I probably have the same books you do- and cannot find anything definitive. I suspect a lot of us are in the same boat. Looking at photos, there was clearly a lot of variation. Here are a few things that appear to me to be more or less factual, based on photos I have seen-
Which is to say- everything below is my own personal opinion, your mileage may vary, this tape will self destruct in 10 seconds and the Secretary will disavow any knowledge of me ever saying a word of it. Anyway, as we all know, the best way to get a historical society to bring out a book with specific information, is to build and paint a model without having the specific information.
A few cars, such as the "Ice cars" (reefers used to transport ice for company use) were "battleship gray". I think that this may have been literally true- as in military surplus after WWII. Whatever it is, the photos look darker than what is used on most MoW cars. Generally, I would suspect that "light gray" may also have varied shop to shop, and year to year. That said, also clear that sometimes large quantities of equipment were run through one shop at the same time- and photos would indicate that the crews took pretty good care of their own equipment.
Some former passenger cars were left in either coach green or painted with any one of the grays used in either the 2 tone scheme of the later all gray scheme. Some freight cars were used in mineral brown paint at least until they could get it to the paint shop.
Most ex passenger cars (especially the 97 old sleepers purchased in 1953-56 from Pullman using ATSF's credits from the Pullman breakup) appear to be a color that I can best describe as "aluminum gray" or "non-metallic aluminum". A couple model paint companies make such colors. In any case, a very light gray on the sides. In the Sleeping car book, there is a pic of one of these cars from Dec 1956, and the roof coating does appear metallic. Not as bright as the "silver aluminum" used in the 60s, but clearly more reflective than the sides. I am speculating here, but given that the "Paint and Lettering Guide" shows a car circa 1949 with a black roof- and to my eye, the sides are a darker gray than used on the 1953 lot (maybe the late 40s car is "faded battleship"?), I would speculate that the painting of the former Pullman cars marked the beginning of the use of metallic roof coating. Of course, not all at once- and that car with the black roof in 1949 probably did not go through the paint shop again until the late 50s or early 60s.
I think the origin of the "light greenish gray" and some of the variation of color may have to do with the paint underneath being either pullman or coach green, or mineral brown- so cars that were painted light gray would have tended to darken and "tint" toward the shade underneath as the dust of Texas and sand of Arizona and California "sandblasted" the light gray paint.
Anyway, if your cars end up a "light gray" of your choice, with perhaps a mix of roof coatings as appropriate, and the occasional "battleship gray" car, and generally look like a car from the Painting and Lettering Guide, I won't find any fault, and would guess 99.9% of modelers will just be admiring your work on creating an MoW consist.
Again, please remember this advice is free and worth what you paid for it.
Tom D
