What do all these cats have in common? They are all female. All calicos and tortishells have both black and red in their coats. These colors are expressed exclusively on the X chromosome. The Y chromosome is smaller and doesn't contain as much information.

Orange, red, and all variations are dominant. The gene for this is O. The gene for non-orange is o. The orange gene will cover the whole coat unless there is a presence of an non-orange gene. Then the orange gene will only cover patches while black, chocolate, brown et. will cover the rest.

As you can see nature is geared towards producing lots of tortieshells. Calicos are tortieshells with white spotting. Why tortieshells? I believe that the dappling effect, like Eve's, gives good cover in darkness. Eve is invisable at night. Especially against dark backgrounds and shadows.

As for male tortieshells, there are a few. They are not worth money however, except that Japanese ships like to carry male calicos for good luck. I do not know whether or not they would buy one. The reason for male tortieshells is a sex gene anomaly of XXY. The Y chromosome will give the cat male genitalia, but the two X's will make him sterile and reluctant to mate. So male tortieshells cannot be used in any breeding program.