Howdy do, Tom!
Indeed Olive Green was the BLW's "standard" color for steam locomotives. If you wanted Basic Black, you had to ask specifically for that.
I've seen the BLW spec books on Sierra RR 28 & 34. They were painted olive green from BLW.
The DRGW specifially noted they wanted the 480's basic black. The green jackets came along later.
And to answer Senor Craft, "running gear" refers to frame, spring rigging, drivers, etc. Everything but rods and valve gear. 'tis an FRA (ICC) no-no to paint rods because it hides cracks.