I doubt very much if
Melanie Wilkes in "Gone With the Wind" was named "black".
Don't mean to be picky, but why not? I don't remember anything "red" that goes with
Cathy Scarlett O'Hara. Besides, the name was already in use, so the author might have just picked it without any reference to its meaning.
Btw, it happens that when a foreign name is introduced in a culture, people tend to translate/derive it from their own language.
An example I have in mind: the Greek name
Tycho ("hitting the mark") is commonly perceived in Bulgaria to mean "quiet" from the Bulgarian "tih" (pronounced the same way as "tych"). So, the French-speaking people might very well believe that
Melanie comes from "mel." Is the book you read French?