Best edible paint to decorate a cheesecake?

I am making a homemade cheesecake for my mom this Mother's Day and would like to decorate it with sugared edible flowers; I'm thinking some pansies, rose petals, and some day lily petals. But I would also like to paint some decorations on it as well. What is a good edible paint to use that I can make or buy? I'm trying to go for a watercolor look if I can.