Thanks for the compliments Tom on this one. But I think my thoughts on these various interior colors are very close to being correct.
They built J model B-24's in 5 factories instead of only 2 like you mentioned. This is what they have to say about it at Wikipedia. Other books have the same information in them.
Besides being built by Ford at Willow Run, the Consolidated planes were being built by Douglas, (using Ford Parts) in Tulsa OK.
Bell aircraft Company also built them under license in Marietta GA.
North American built them in Grand Prairie Texas as well...
In fact, quite a few (estimated at 801) were built in the San Diego Consolidated plant using parts that were trucked in from Ford. These sub assembly kits were called "Knock Down" planes...
Most of these sub assemblies were made using parts from various sub contractors. These two pictures here came from the Chula Vista public library. They show engine assemblies and superchargers being produced nearby. These "sub" assemblies are just one of the many that were provided by the "sub contractors" I mentioned. These engines were built at yet another factory... Logistics. And a lot of it. These smaller sub assemblies were assembled (and sometimes actually produced on site) at the 5 locations I mentioned above.
Ford was by far the biggest producer... but it took an awful long time for the Willow Run plant to get moving. Once Ford did reach it's peak production, it was producing a B-24 every 59 minutes or so... Simply amazing.
Ford also assembled these "knock down" planes using parts from the subcontractors. Once the major assemblies were completed, they were trucked off elsewhere to other plants for final assembly. Using turrets as an example... Sperry, Emerson, Consolidated, you get the drift.
This fact that they used a lot of subcontractors, combined with the various specifications and color call outs made by the US Army Air Force for interior finishes and specs for anti glare measures for crew compartments are why these planes were painted the way they were.
Here's just a few pictures that show these assemblies before they were "bolted together" literally... You will see that the joints on these larger components match up almost identically to the different colors I used on mine. These larger components would have had various colors used inside them, but would have had an overall theme of having a similar color throughout the sub assembly.
When you consider that various paint manufacturers would have been supplying paint to these sub contractors, and that the paint would have came from different lots, you can see why there was a variation between units. They had specifications for colors, but that's another can of worms.
This is why there are 3 different colors that I used on my build.
There has been a lot of research done in more recent times on the various shades of green that were used by other authors such as Dana Bell. This is a fascinating subject, and more work needs to be done in this field. No longer is it "correct" to just paint on some interior green if you want an accurate model.
I have a partial copy of the specific color specifications that the USAAF called for on the B-25. This document shows that in some locations that bare metal finish was good enough... and that no painting was required on some parts. Instead they relied on the anodized finish of the aluminum for corrosion control. The same treatment was given to other Army bombers such as the B-24.
The same thing happened to other US Army aircraft, just like you mentioned. The P-47, P-51 etc., all had variations of different colors used throughout the airframe. This would change with time, throughout the production history of each specific type.
So you were partially correct too... 🙂
Please stay tuned, as I hope to get some more work done on this one while the other kits on the work bench are drying...