Painting anything white with watercolour can be a little tricky. Essentially the idea is not to paint the white object, rather to paint its shadows, with the palest of greys and blues and purples. The last time I did this it was for daisies, and the whole thing got me quite philosophical.
Today Miriam is helping me again. This particular cat is Frosty. He (or she?) is the subject of the second project in the online class called Crazy Cats. Still haven't quite got the hang of the fine white whiskers... but I'm working on it!