Always girls from what I recall reading decades ago, genetic stuff. Someone figure out a way to breed male calicos, and hit the jackpot.
There are occasionally male calicos; but I read when it happens they are sterile because of the genetics. My mother had a male calico, he never reproduced. People always say a male calico would be worth a fortune but since they can’t reproduce there really isn’t any real interest in them that I know of other than novelty.
The gene for color in cats is carried on the X chromosome. In cats, some cells could have the gene for black activated on one X chromosome and have the gene for red activated on the other X chromosome. So random cells are either black or red (orange), since female cats have 2 X chromosomes. Males only have 1 X chromosome, so they are either black OR red, not both. If you run across a rare male calico, he is a chimera and probably has abnormal chromosomes, likely the result of 2 eggs fusing, so he is XY/XY instead of XY
Doesn’t work that way. The black and orange genes are both X-linked, so a male Calico or Tortie can never pass it on.