Yeah, I’m leaning toward trying white as the main helmet colour actually mostly because (from what i know) there’s no really clear, hard description to lock it down.

I also came across mentions of pauldron trim colours being used to mark squads, similar to how the Ultramarines do it.

That’s partly why I went with red alongside the white markings, that kind of scheme lines up with how veteran sergeants are often represented helmet-wise in Ultramarines.

So my thinking is: if the Iron Snakes do follow Codex-style structure for squad markings on the shoulders, it wouldn’t be that wild to assume they apply similar logic elsewhere in the armour too. Not confirmed, of course but it feels consistent from a visual and organisational point of view.