Butterscotch smoke?

[Edwin Frey]

I've noticed that during the past few days when the locomotives are sitting idle, when coal is shoveled in to keep them hot, the smoke is distinctly orange. Are they burning a different grade of coal now? What would cause that strange color?
I've also noticed that when the locos are really working, pulling a load, the smoke appears to be the usual black.

[Tom Casper]

Edwin, that is a sign of a banked fire. very low air supple causes the coal to give off a lot of unburned gasses with more yellow smoke as there is sulfer in the coal. Not sure of the orange other than a less intense fire burns orange. Maybe a tech person can expand.

Tom C.