A friend of mine thought she made a fashion error with her black and brown outfit, she wore a black top with brown pants, to me it looked pretty chic. I don't have a picture of her outfit but I do have pictures that prove that black and brown DO work well together.
however, black and brown don't always go together! like every color, we still have to be careful with mixing and matching them. it's kinda like mixing purple and green, sometimes it works, sometimes it doesn't.