Mark5: Thank you. I saw the GS gons, in both colors, so, as Jason says, I'm not going to take them as proof.
I model the early BN, with emphasis on GN, and they did the opposite with their 2-bay open hoppers. Those came in freight car red/brown (at least three lettering styles), Vermillion Red (2 styles), and black (1 style that I know of) BEFORE they switched to Big Sky Blue style lettering on black cars.
52'6" gons were Vermillion or black. Older 65' gons seem to have been freight car red/brown or black. Their newest ones were Vermillion. Some of the 52'6" cars eventually received BSB lettering on black.
No consistency at all, and looking at one type of car wouldn't be much help.