Dear all,
In my experience the frames would be outsourced and delivered to the assemblty facility in an etch primer (red,yellow,grey),same as some lorry frames etc,they would then assemble the loco,and then spray paint the livery,so only the outside of the bogies would be sprayed black etc and the body work in whatever colour,and the undersides are left the etch primder colour.Later on in life when loco's are revamped etc they usually steam clean the undersides and spray everything the same colour,black,or whatever takes their fancy,I have even seen white!!The engine bay gets the same treatment and everything gets sprayed including fan belts,batteries,everything,just to make them look new/revamped,also water hoses and evrything gets the blow over,after a few hours of running you get the paint burning of the manifolds and cracking on hoses and cables and it looks a right mess!!
so called "reconditioned"