As far as heraldry goes, I think having a crimson shoulderguard suffices for the basic mercenaries (while leaving the rest of the armor black or unpainted). Officers could be distinguished by more red. The more red you have on your armor, the biggah boss you are. Thoughts?

Since we're already referencing WH40K Orks, we might as well steal their basis for organization: the biggest, meanest, but especially the most cunning orcs are the boss. In this case Nar Mat Kordh-Ishi was founded by orcs who have experience fighting with/against humans, so the orcs who know the most about tactics and drilling discipline into the others are at the top of the food chain. I like the idea of our characters being part of a first company, the nastiest of the bunch. The rest of the company can be divided into squads? Are we officers in charge of some of these (elite) squads, perhaps? That leaves room for us to develop some NPCs to interact with and boss around.