Realistic steel? There's nothing unrealistic about blackened or blued armor. In fact, polished steel would have been rare. Aside from expensive man-power to polish your armor, once you polish steel, and leave it blank, it rusts like crazy. Mind you, this is high carbon steel, not stainless. That means spending a lot of time maintaining armor every day. And if you're wearing armor, you're probaby at war, and you have better things to do with your time than sit around polishing your... armor.

Typical treatment would have been, if I'm not mistaken, via linseed oil or scale-blackening and resulted in a bluish or grey armor color. I believe painted armor was not unheard of as well.