White Pass / Army Caboose Colors?

I was hoping that someone here on the list may be able to shed some light on a question I have.

I've been trying to determine what color the Army Transportation Corps cabooses were while operating on the White Pass during the war. Specifically, the two C&S and the one Silverton Northern (ex-DRG) caboose - in every photo I have seen of these cars in operation (what few there are) they seem to be very dark in color when wearing the "USA" lettering.

I've had one modeler tell me that, per standard practice, these cabooses would have been painted all black, with white lettering... and while I can see that fitting with the B&W photos I've seen, I also know that operations like the Sumpter Valley have painted "rail fan" equipment red, rather than black when representing the USA cabooses...

Help?!

Thanks in advance,
Josh