the mark of Cain?

I read this book recently "sled hill" by Chris Crutcher. I met the author and made some questions. but that was before reading "Hill sled" So I couldnt ask my question. book's main character is Eddie. in the last three months has suffered the death of his father and his best friend. was the first to find both. because it has suffered so much, the minister of his church wants to be baptized and come closer to God that to recover from the tragedies. before being baptized, the minister required to take classes. in one of these classes tells Eddie that God put the "mark" of Cain after he killed Abel. then the minister even said that the "brand" is that their skin color. The mark of Cain was that God made him black. Is this true or is it just the author is making?

Cain being black is a theory that some people have, and mostly use it to discriminate against black people. I've heard of this "reasoning" many times in my life. In truth, however, nobody knows what that means "mark" was. If it was not. I think there was.

The Sledding Hill