That looks like normal patina to me. I have a pair of Aldens in brown chromexcel that did the same "nearly black" thing, and other areas where I was sure I had scuffed them permanently. My black wolverines would scuff deep enough for brown leather to show through. They always returned to normal after a quick wipe with a conditioner. I use Lexol but practically any boot oil should work.
3/14/15 at 3:42pm