Boiler Jacket Color

As I was helping my lovely wife repack all of our stuff over the weekend, I ran across a copy of my book I picked up years ago about Memories of the Narrow Guage Circle or something like that...
Anyway, they have a pic of 497 just after she had been outshopped from Salida and the caption, while talking about the f stop and aperature setting for such a regal pic, also mentioned that the boiler jacket was Olive Green.
It also mentioned that the 497 was pulling an excursion that day. Maybe someone knows more than I but which is more maintainance intensive, black or olive? I know they make black that is heat resistant....
I guess it all depends on what time period we want to represent doesn't it?