I love that middle girl!! She is gorgeous! Would be a perfect mate for him!
Heres a piece from an article about dragons from Betty Splendens
What genes determine the "dragon" phenotype?
We can clearly see that the unique appearance of the "dragon" clearlyaffects the iridescent layer. So far several genes have beencharacterized which affect the iridescent layer, for example theclassical iridescent colors steel blue (blbl), turquoise (BlBl) androyal blue (Blbl), metallic or yellow reflecting iridophore (thewildtype variant of the reduced yellow iridophore locus)  and thespread iridescence gene (Si) which is responsible for the increase indensity and distribution of the iridescent color.
In 2007, Joep van Esch of Bettaterritory.nl made some experimentalcrosses with "dragons" in his fishroom in order to learn more about theheredity behaviour of this trait (see pedigree below). After crossing a"dragon" to a regular metallic (BT171007A)he observed that all offspring had a copper phenotype. Considering thefact that a copper phenotype (homozygous metallic steel blue, blbl ++)can only be obtained when the offspring obtains one steel blue (bl) andone metallic (+) allele from each parent , this result suggests thatboth traits may play an important role in the unique appearance of the"dragon" phenotype. Interestingly, the metallic scaling of theoffspring seemed more thick and solid than observed in regular metallicfish. This characteristic was also passed on to the offspring when aheterozygous "dragon" was crossed to a heterozygous metallic fish (BT271107). The offspring resulting from crossing two heterozygous metallic sibblings (BT171007B)resulted in homozygous, heterozygous and non-metallic offspring withoutthis unique appearance which was observed before. Off course we have tokeep in mind that these findings were purely based on macroscopicobservations (with the naked eye). Nevertheless, these crosses showthat the "dragon" trait is hereditable and suggests that it behavesquite dominant as it already clearly affects the iridescent layer inheterozygous fish.