I wondered the same but then again I've seen many too bright acolytes (even if it matches the mask). So I might experiment in my own direction.
When I look at the videos I imagine the artists chose a different material than the Jedi armor counterpart, and I believe it isn't regarded as a metal armor. I will try a few paints I find on scrap abs but I'll definitely go for the reference material look rather than follow the CRL at risk for not getting approved. In-game the armor is way more black and the undersuit isn't much darker than the armor at all in the trailers, unlike the robe. I think silver paints are more of "realism freestyle". Like overweathered E11's though the screen used were not so weathered at all. But in this case if it is metal armor, I would say a dark dark gray would be close. But regarding silver layer under another color I choose to believe canon-wise it wasn't a silver armor that the dude took out for a layer of spray paint. It seems integrally black.