This was happening when Mythos had first hit closed Beta (before FSS went down). I had old screenshots of grey (broken) keys, pots, and map scrolls.
Also, I currently have a green key sitting in my stash as we speak so apparently the color bug still exists and was never fixed properly. I can screenshot it tonight if anyone is interested in seeing a green key. Though I do like the idea of attributes on normal items, like an Epic potion which gives more life, or gives mana as well, or extra duration, etc. Maybe a green Key can have two uses instead of just one.
Just a thought. Rather than patching it out, why not stray from the norm and make rare common items like keys, scrolls, charms, etc.?