Royalty dlc does this exact thing with the prestige armors! (You'll find them at Royalty/Defs/ThingDefs_misc/apparel_various.xml), the shader type and the worngraphicmask bits are the important parts in achieving the thing you want, if I remember correctly, as I've not done this myself in maybe 2 years my memory's bit hazy
and the art source files should have an example of the mask graphics you need to have for them
https://ludeon.com/forums/index.php?topic=2325.0
and the art source files should have an example of the mask graphics you need to have for them
https://ludeon.com/forums/index.php?topic=2325.0