Personally, I think there’s a real missed opportunity in designing cosmetics based on Astarte’s legions, as there are 18 legions all with unique cosmetic designs to choose from.
I think GW will veto that instantly, since space marine chapters are notoriously touchy about people that are not them using their chapter’s heraldry and colours, and Fatshark has stated they are keeping space marines out of Darktide as much as possible.
TBH I’d rather be able to paint my gear the way I want it, even with a limited palette like Warframe, but then how would Fatshark sell recolours? Another customisation feature gone the way of feeding the MTX monster.
But how would you stop people from painting Astarte colors if GW would veto it?
All jokes aside, yeah the in game cosmetics could use some love considering how lore rich the 40k universe is.
I would still put that under colours, and hazard stripes tend to be a very popular colour scheme outside of Iron Warriors too, like Necromunda, Orks, Votann, GSC. The scab shotgunners have hazard stripes too for some reason.
Like black and white colour scheme is probably fine, but if you start plastering iron crosses everywhere too and you might get a visit from a Black Templar crusade fleet at some point.
Although, there definitely are some regiments that deliberately invoke a lot of flavour from an Astartes chapter, like the Ultramar Auxiliaries have a really strong Roman legionnaire flavour to match some of the Ultramarine styles.