Just remove the Nord Nobleman Shirt's black part
That's not how armor works in Warband. Armor overwrites the body mesh and replaces it with the armor mesh. You make it sound like armor is added on top of the body, which is not the case.
There are two ways how to get armor show skin dependent on the character model. One is to define a new dynamically colored texture space similar to the heraldic items, which get their texture from the banner in use. The other one is adding an armor class that adds itself on top to the body's mesh instead of overwriting it. If you can figure out how to do either and deliver code, skin showing armors will be possible.
In summary, my research concludes that 300 is not a battle movie, but gay porn. All evidence, first and foremost the frequent closeups of Leonidas' gluteal cleft, provides strong empirical support this thesis. This paper may be prone to researcher bias, because unlike other males, I do not start drooling uncontrollably at the sight of beefcake and homosexual interaction by means of various novelty insertions. The resulting practical implications for research and management recommend agents to rationally abstain from associating themselves with 300-related material, since the concomitant social stigma translates
ceteris paribus into a loss of utility.