Normally, only female cats have the tortoiseshell phenotype. this is most likely because

Females have 2 X chromosomes as males have one x and one y. The two X chromosomes may carry different alleles for hair color. On one x it may be black on the other x it may be orange. Usually in females one of the x,s is turned off in each cell. So this is why you have female cats that are calico colored meaning some orange some black. The black Allele might be turned on in some parts of there coat and vs.