Watercolor.
Witch familiars are a relatively recent addition to witch lore, becoming a popular proof of association with the Devil during the witch trials. He or another witch would have gifted the accused with a cat, a toad, a weasel, a rat… to help with dark work & suckle at her “3rd teat” (could be a mole or a skin tag). For some reason, today’s self-proclaimed witches seem to be able to personally select their familiars and almost exclusively go for cats.