Because males have only one X factor, they will be either orange or non-orange, but never tortoiseshell. Little's theory also explains the common observation that ginger cats are mostly male.

This is what makes male cats ginger, and is responsible for the orange splotches on calico and tortoiseshell females. The two studies are published as preprints and have yet to be peer-reviewed ...

ORANGE, or ginger, cats are much beloved around the ... Conversely, calico or tortoiseshell cats are usually female – the female’s extra X chromosome allows the possibility of her receiving ...