Koi angelfish are blushing gold marbles. They may be either homozygous for the gold marble gene (Gm/Gm) or heterozygous with gold (Gm/g). Homozygous individuals usually have more black than heterozygous ones. There is considerable variation in how koi "express" ranging from black and white fish often referred to as "Panda Koi", through typical black & white fish with orange or reddish crowns, on to fish where most of the body is covered in orange. Despite this variation, as the factors controlling the variation are not fully understood all koi are described genetically as Gm/g S/S or Gm/Gm S/S.