Accuracy might vary, but in my Deathwatch
RPG book, by
FFG, their example Apothecary has the typical, black suit of the Deathwatch, and the silver arm/vembrace on the left side. The "I'm an Apothecary, I wear white" is reflected in his helmet, his backpack, and his narthecium, on the right arm, as well as the various Apothecary symbolisms, and embellishments. His right shoulder also advertises which Chapter he hails from, left knee, too.
Certainly, artistic license can weasel in, lots of places, and this is the same game that once had Craftworld Skittles Eldar ("See the rainbow. Be aced by the rainbow!") some decades ago, so a bit of garish color is par for the course. I won't say Fantasy Flight Games actively sat down with
GW, and that they cleared every art choice, but it's a pretty good representation, in my opinion, if maybe simply their own artistic license, but they have a bit of the license to "officially" make stuff, so it feels slightly more justified, to me. The Techmarine follows the theme. Black armor, silver left arm, Chapter logo right shoulder, and his helmet, backpack, servoarm, and right knee are the red of Mars, with proper logos. Librarian subs in blue on the pack, knees, and part of the right shoulder (no helmet in that picture).
Well, hope that helps. if not, best of luck, regardless.