Just to put in my own thoughts:
It is tasteful to match if you can; many people have told me that if it's all you have, wear it with pride.

I am currently waiting on a brown set of accessories, but only own black shoes (it's all I am allowed to wear at one job), but I am also waiting to get enough funds to grab a pair of brown brogues...which I plan to wear along with my brown leather ensemble. I have been told it is a nice way to clean up, but not formal, despite the fact that I plan to wear this set to a all clan banquet next month... it's all I have besides an inexpensive black sporran, and a slightly wider than average belt (NOT a kilt belt though)... so while not formal, it would be the best that I have... since all my other gear pales in comparison (aside from kilts... I have a couple options there). I am also considering getting a pair of brown leather Dr. Martin's style boots to go with the brown stuff for a more casual look (I need another set of boots anyhow)... it's just a matter of tastefulyl coordinating what you have in my opinion.

I have also read that brown used to be issued to regimetal officers (brown apparently being the better quality stuff at the time) for their belts and sporrans, but they were issued the standard brogues (black). So as far as that goes, I would say that there is some leeway to be had.

I honestly wouldn't worry too much about matching shoes for the moment, unless you have the disposable income to throw down for a pair, then I would say go for it, just for the sake of having variety.