John,
There were instructions to paint the boiler jackets green. See attached image. However, whether it was ever really done on the narrow gauge to any great extent is still not clear. I wonder if the practice was generally confined to the standard gauge like the tri-color herald. The only narrow gauge locomotives that I know that were green for sure were 489 and 499 which were painted green for RMRRC trips out of Salida about 1949 to 1950. Also, 340 appeared newly shopped in green paint at Montrose about 1950. I understand it never ran in this paint job, but was sold off to Knotts. Jerry Day says he has looked at all of Dick Kindig's color slides and could not find a single picture of a narrow gauge locomotive with a green boiler. Perhaps he can add to this.