My biggest gap in Scalecoat is Big Sky Blue. On the other hand, Floquil's wasn't all that accurate, nor was Polly-Scales, AND they didn't match each other. For mod 70s freight cars it doesn't matter much, as the color changed with age, and every car seems to be different.
The MS suggestion for BSB was Model Master "French Blue". I tried it, and Tamiya "French Blue", they're not the same, and neither is close to the GNRHS color chip. Oh well.
I've asked the new owners of Scalecoat to add Big Sky Blue if they add any new colors. That will have to wait until they figure out how to package spray cans with the yellows, oranges, and greens that are giving them trouble. Something in certain pigments reacts with the propellant and causes the cans to literally explode. Apparently the suppler changed the pigments a few years back, and won't say what the change was, as pigments are proprietary.