Far as I know, you need a Blue Dempsey bred to a normal Jack Dempsey which carries Blue Dempsey genes(usually sibling, and usually not for sale was what I found in articles) to breed Blue Dempseys. Therefore, it is because of this that it is supposed to be very difficult to breed Blue Dempseys. Not sure if it is still like this. This was what I read about Blue Dempseys when it was introduced not too many years yet.