Albus maybe? It does mean "white". Or maybe Alba would be the female form, if you're talking about a female kitten. I'd suggest Luna but you say that name's already taken sa pamamagitan ng a black kitten.
Here are some suggestions: 1. Minerva (meaning; goddess of wisdom and war) 2. Ginerva or Ginny (derived from celtic origin) 3. Bellatrix (meaning; female warrior) 4. Ariana (meaning; very holy) 5. Narcissa (meaning; daffodil) 6. Nymphandora (meaning; divinty of nature) 7. Tonks I personally prefer the name "Minerva", minnie for short.