Based on their colors, I would go with names that represent the sun and moon. Assuming they're siblings, having names that indicate they're a pair would also be fun.
Luna(black) and Celestia(blond) if they're both girls. Especially if you're a fan of MLP
Salem(black) and Sabrina(blond) if they're a boy and girl respectively.
Twilight(black) and Dawn(blond) would be another great pairing for two girls.
And if the black one is a girl, but the blond one is a boy, Luna and Artemis. Though, Artemis also works for a girl.
Sorry, I can't tell their genders, so I wanted to give some options.
I always wanted to have a black cat and other pet so I can call one of them licht and moon
Licht mean light in German and licht moon mean moon light :3
Spaghetti and Meatball