Well, I knew sooner or later the color scheme was gonna open a can of worms.
Speaking as one who spent a lot of time cleaning and scraping this unit, there were three layers of paint. Bottom was green, as you see here. over that was yellow (a medium, nondescript yellow), probably "safety yellow" originally. On top of that was the faded grey/black (maybe charcoal gray) that was on it when it was donated. Admittedly, the black radiator and grill is a departure from the original. It is remotely possible that there was an earlier layer of paint, but if so we found no trace of it in any nooks, crannys or corners. I'm going to go out on a limb here, and suggest that the lettering was probably red. I base this assumption on the fact that hunter green with red lettering was a very common combination on heavy equipment of that era. much as Caterpillar Yellow is today. Witness it's use on Oliver and Hart-Parr tractors, Fairbanks-morse stationary engines and other iron from that time. When our Whitcomb was built, it did not have the cachet of a true railroad locomotive, but was considered merely a rail tractor, not much different from a Holt, Best, or other heavy implements common at the time.
Based on my own observations, Jim Witherell's research and common sense, I believe the color it carries now is an accurate representation of the way it looked when it first came to Baker.
Jeff