A cat needs to have pointed coats in order to be Siamese, and this happens thanks to the Himalayan gene. Since all of these cats have some form of albinism, it is impossible for a Siamese to be a black cat.
The Himalayan gene is heat sensitive and causes albinism. Siamese kittens are all born white due to the high temperature in the womb. After the kittens are born, their bodies are exposed to colder temperatures, and their coat color starts to show up.
Yes, and that cat is called a seal-point Siamese cat, but most of the fur will be gray or white. A black cat might also be part Siamese if it was mixed and had kittens with other cat breeds that don’t possess recessive genes.