Hello Walter
I tested some things, and used some different colors, created material with colors, also in the designdata.
what I ended up with was one part (angle 32140 yellow) to be green (color I gave it, in the back and grey in the front.
so the same part, but in different assemblies.
so I stripped the main assembly until it only had two sub assies: etape 1108 and etape 1081, adn than it was oke, but much less components as you already sad.
So I did this with Inventor 2016.2.2
I also tried editing the color of one 6632, but the other one did also change..??
when you use the third option you get a multibody part, and you can look at the bodies and below that the part. this last one has the color, but with the same part in a diferent location it has not the color so this is inconsequent behaviour. I also looked at the design views but can't find it, so I geus this must be a Bug, something for Autodesk.
I also tested it in 2017.2.1 and there it work fine...!!! so maybe that's the solution?
If this answers your question then please select "Accept as Solution"
Kudo's are also appreciated
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Succes on your project, and have a nice day
Herm Jan