Postwar motor armature windings

The green wire is just another enamel-like insulator found in later models. I'm not sure of an exact transition. Functionally the same as copper color. The relay next to the e-unit is a whistle/horn relay. It is activated by a DC carrier/offset on the AC track.

Sorry for the poor cinematography! Hard to hold I pad and control train! Lol

I've got some experience with PW geeps and FMs. Green motor windings came into being (I believe) somewhere in the early 60s, perhaps even a bit in the late 50s. My Virginian 2322 had green windings on both motors-original. Other than the color of windings on the first pic your B&M GP9 runs like the best of my earlier Geeps. Skol!

PS: Brian Moran told you about your whistle relay (horn). Why don't you stick a new "D" cell battery under the shell (which looks to be in VG shape) and test your horn? Some of the Geeps have a really nice horn sound but you may need to clean relay contacts, etc., for dependable horn-ing. If there's trouble with it blowing or the tone seems high and unnatural, you may need to spend an hour on YouTube learning how to get a horn to blow and adjust it for best sound. It's not hard... Here are a couple of videos that show you how to get them blowing. The first one's just about horns and the second's kinda tekkie, but shows you what can be done !                          <https://www.youtube.com/watch?v=3LsDKsNBBKQ>          <https://www.youtube.com/watch?v=JmZX6t12EGU> 

Sometimes Manufacturing plants use different color insulation on different gauge wires. This makes it easy to check wire gauge.

Sorry to tell you but that frame is repainted. They did not mask off the areas that ground the motor, lights and the battery contact. That is why there is a yellow wire on the light bracket rivet to the motor housing .

Hmm, repainted frame ? thank you Lionel Parts, This is a good detective observation. 
I was in fact questioning the validity of the drive  components. 
but now I wonder if the frame is postwar at all?  Additionally, there is something unusual in the fit of the shell to the  repainted chassis. While my new observation is not on the drive components I have just posted an inquiry of the chassis to shell alignment.

Virginian65, thanks for the horn repair links.