What does it mean when a girl wears black panties?

Answer 1

It may, of course, not be intended to mean anything, but black underwear and Bras are generally considered very sexy indeed. The message conveyed is that she is a sexy and daring girl.

Answer 2

The color of a girl's panties doesn't have a universal meaning. It could be as simple as a style preference or what was available that day. It's best not to read too much into it.