The marble gene can do some crazy things. I've seen pictures of a fish who was dark red with a big patch of bright blue right in the middle of him.
It's crazy because on some fish, the marble gene doesn't move (as in the colors won't change) but on others the fish constantly changes color it's entire life. That's why marbles can be so frustrating to work with if your breeding for color.
*Be smart.. Do your research!!*