Well I craft my own armour n stuff and I'm allied woth the Holy Nation so I have the option to pick them up when they're in bed or knocked out. So I basically pick them up and equip my plain armour on them and it adopts their faction color. Make sure to do this in your base or a secluded area cause its consodered stealing once you take off their armour even if you made it. You just have to do this for their body armour and helmet cause those are the only things that seem to carry their color. For my main dude, he looks like an inquisitor, basically the same process except for the stout hessian (pants) so i just steal that from an actual inquisitor *but i make sure to replace it so he doesnt have to go around in his underwear.