The X and Y chromosomes not only determine gender (XX = female, XY = male), but they also carry other inheritable traits as well.
In cats, the coat color red is carried on the X chromosome and exhibits sex-linked inheritance.
The presence of the orange gene
on the X chromosome explains why it is more common for male cats have red coats than female cats.
Since males only carry one X chromosome, they only need one copy of the red gene to be red in color.
By contrast to be red a female would need carry red on both X chromosomes.
Then what about a female with red on only one X chromosome? These cats are both red and not red (e.g. ‘black’). This leads to the so called tortie (or tortoiseshell) pattern. In a tortie cat, each of the cat’s cells that can produce hair or skin pigment, can express accidentally either the red color or the non-red color, giving the characteristic mottled coat pattern of the tortie. In siamese and balinese, the red or tortie colour is only visible in their points. The dilution of red leads to a creme colour, which is also possible in females as blue-creme-tortie or lilac-creme-tortie. Moreover tortie-tabby patterns in several colours are also acceteped.
Contessa von Manderley, Balinese seal-tortie-point