Longer answer:

There are two possibilities. Snowball had four white kittens last time, which is pretty improbable since the stud cat is blue. We know from genetic testing (both cats have been fully tested) that the possible colours are:

Blue (like Dad and Mum*)

photo by westpark on flickr

White (like Mum*)

Snowball by Rubistyle.com

We’ll only know for sure when they arrive in mid-August!

* White isn’t strictly speaking a genetic coat pattern. The gene that makes a white cat white is a “masking gene” and masks the cat’s true genetic colour (that’s why white kittens have spots of colour that eventually disappear). According to Snowball’s breeder, she is blue underneath all that white.