Tortoiseshell is a coat pattern, not a breed. Black-based and orange-based colors blend in patches or a fine mottle, usually with little or no white. Dilute torties show soft gray and cream, and torbies add tabby stripes. Nearly all tortoiseshells are female because the orange gene sits on the X chromosome, and the rare males usually carry an extra X.
Most torties are domestic shorthairs or longhairs, though the pattern turns up in Persians, Maine Coons, British Shorthairs and many other breeds. The "tortitude" reputation rests mostly on owner impressions, so a cat's age, history and socialization say far more about personality than color. In Fort Collins, that means a tortie can be shy, bold, cuddly or independent, and the best match is the cat whose habits fit your home.