Chicago and North Western GP40 5516 from an Atlas model.
I stripped a factory painted unit, and redetailed the shell with a new bell, lift rings, all weather window, added Kadee #58 scale couplers, etc etc.
Unit was abrasivized and then washed. From there, it was primed with Floquil primer, the yellow is Testor's Model Master Cadnium yellow (for fresh Zito yellow...didn't last long like that), the green is Polyscale CNW green. The black is Floquil engine black. The decals are by Microscale. The entire unit was then clearcoated with half Testor's dullcoat and half Testor's glosscoat thinned with lacquer thinner.