Let me add another vote to wear your black boots, and to wear black belt and sporran with them. I would say black or brown leather is fine for casual wear, but black for formal wear. Boots would be fine with a t-shirt, polo, or sport shirt; dress shoes if you plan to wear a tie.

In the end though, it is you who must be happy with your look, as others have said let the mirror be your guide.

Post some pics when you get it, and you will have no shortage of opinions.