Today (9/16) I purchased a stock car kit a local train show. Speciffically an Athearn stock car, NP railroad. The underside of the car is black plastic and the car weight is exposed bare metal. Does anyone have info on the prototype colors used on NP freight cars? Possibly they were the same color as the car body but I would like to be sure. To any manufacturers reading this. It wouldn't hurt to add this info to your instruction sheets.