White or Aluminum?

Gang,
Another model building question. Was wondering if the concensus would be for aluminum or white paint on the edges of the locomotive running boards. I've got a copy of the origional specs posted recently, which indicate aluminum. But many of the color photos and models I've seen have them in white. Is one color perhaps more correct for DRGW and another for C&TS or D&S? Or did the DRGW change to white in later years? Or was it up to the various paint shops?
Lastly, have seen some photos where the outside tender sills appear to have been silver. Or was this perhaps just discoloration from ash and dirt accumulation? Thanx again, Gary