For my dudes, I've chosen metallic silver as the sept color. I'm sure I'm not original, but the color is sticking. I just wanted to double check before I go spinning homebrew fluff, that a silver-marking sept doesn't already exist in canon.
From what I can tell, Tau'n is maybe up there. I know that metallic silver is difficult to represent with a single, solid color like they use in the codices when they highlight certain symbols, and Tau'n appears to be a dark grey, but are their colors described anywhere? Is there anyone else I'm overlooking?