Actually, warband has got a built in vertex coloring of some kind(they use to make the black face and body texture), which means it's possible to make an ingame slider where you choose the color of the armor yourself.. The texture sheet just needs to be white, then it gets applied with a vertex color that changes the models color or something. If you check out the Bear Force II for warband they got an armor editor like that! 
Edit: Another possible way to do it is to make the part you want colored a tableu-item, meaning it applies the texture of your banner, thus letting you kinda choose the color at least.
Edit: Another possible way to do it is to make the part you want colored a tableu-item, meaning it applies the texture of your banner, thus letting you kinda choose the color at least.
![[+]](/images/collapse_collapsed.png "[+]")
Spoiler