Dilute tortoiseshell is a coat pattern, not a breed. The blue-gray and cream patches, or a soft marbled blend, come from a recessive dilution gene, and the patchwork needs two X chromosomes, which is why nearly all dilute torties are female. Most are domestic shorthairs or longhairs, usually medium cats of 6 to 14 pounds that live 12 to 18 years.
The folklore about "tortitude" has little evidence behind it. Dilute torties run from shy to outgoing and from lap cats to independent explorers, so meeting the cat tells you far more than the color does. Shedding is moderate, and longhaired cats need regular brushing, which keeps fur from piling up in a small rowhouse.