Well a number of roads had FA1s and FA2s. Not sure which the Lionel shell represents, but since it is more in the toy train size it probably does not matter which prototype.
Three easy ones would be Pennsylvania, Western Maryland (fireball), and New York Central. The Pennsylvania would be very dark green which would go over the black well. Both the WM and NYC were basic black. The striping for all of these are in decal sets I tihnk from Microscale. So one color paint job and decals.
The trucks frame and pilot on the PRR would be black so that is two colors. The dark green is almost black. I mix 4 parts black to one part Scalecoat PRR Brunswick green to it black enough for me.
