Earl:
Combine 212, and coaches 280 and, I believe 284 were all painted at the same time, with coaches 306 and 320 following soon after.
I agree that the rest of the equipment was not painted until 1955, when they all were done for another movie. In that one, the roof color on all the cars was brown. They were painted with Aluminum roofs soon after. The Sundance calendar of two or three years ago had a picture taken in '55 showing the entire consist gold with brown roofs. Weird.
B-7 was probably the last car to have been painted Silver and Gold until the first of the new steel coaches were built in what, '61?
I don't think any of the cars, with the possible exception of the B-3 (we know this car today as the "Nomad"), which was the first "General Palmer" was ever repainted green after being Gold, and that was years after it had been sold to private ownership.
Mike