Others have pointed out that the Duke of Rothesay and others wear black shoes all of the time with kilts, even when the rest of the outfit is more in the brown mood, including the sporran.
Speaking of which, there was a thread a while back with a bunch of pictures of him and some discussion of his wearing a brown sporran with black shoes. I cannot find it now, and the search function is of absolutely no help.

The pictures forum only goes to 4 pages, even though the forum index page shows that there are thousands of threads in there. What happened? I'd sure like to look at those pictures again.