Ahitby: Can't tell you how many variations there have been, but I do have one that was in the GM Demonstrator colors that I've had sitting under the table for about 10 years. I'm finally getting around to having TMCC and sound installed, (can't run anything, anymore, without Command Control) I don't know if the GM demo was ever used on either the Milwaukee Road or the C&NW, but that's going to be my justification for having the engine.
I just think that they're kind of neat looking. Certainly a lot better looking loco than their successor, the GP-7 ever was. That was the beginning of the end of styling on a RR locomotive.
Paul Fischer