When a tortoiseshell cat and a black and white cat mate, the kittens can have a variety of different coat patterns. The most common coat patterns are:
* Tortoiseshell: This coat pattern is similar to the tortoiseshell coat pattern of the mother cat, but it can also include patches of white fur.
* Calico: This coat pattern is similar to the tortoiseshell coat pattern, but it also includes patches of white fur.
* Black and white: This coat pattern is similar to the coat pattern of the father cat, but it can also include patches of orange fur.
* Orange and white: This coat pattern is similar to the coat pattern of the tortoiseshell cat, but it does not include any black fur.
The specific coat pattern of the kittens will depend on the genes that they inherit from their parents.