I have a pair of brown leather knee high boots but I don't know what to wear with them besides skinny jeans? Can I wear black leggings?
Heck yeah! The Beautiful Mrs. 737 wears black leggings with her *Pat Benatar* boots and it looks awesome! *These boots are made for walkin', and that's just what they'll do, one of these days these boots are gonna walk all over you* - Nancy Sinatra
You can wear black leggings that fall above the top of the boots, which creates a seamless look. Skinny jeans, short dresses or skirts with dark tights usually look cool when wearing with leather knee high boots.
Sure, mixing brown boot with black legging is fine.