The Black cat is named Luna. She is the first cat in Sailor Moon and is sailor moon's gaurdian cat.
Artimis is the White Cat. He is Sailor V's gaurdian cat and is also centeral control.
Diana is Luna and Artimis' kitten. she comes from the future in Sailor Moon Super S
and is Rini's/Sailor Chibi Moon's gaurdian Kitten. she is gray.
There was one other Cat in Sailor Moon R, his name was Herculys. He saved Luna from a lot of ally cats by throwing a dead fish bone. He also got chased in the sewer by Zoisite because he was a Crystal Carrier. (There is a picture of him in here, it is the one where it says Salor Moon on the bottom left corner and luna has a big sweat drop and Hurculys is in the sky)
There was also a floating cat head in the second half of Sailor Moon R. Her name was Luna P. Rini used this for her powers. Also in a episode Sailor Pluto came out of it but as a hollogram. She sends the inners to rini's dream becasue the doom fantom was controling her dream and was going the capture her.