Little Gluttons

Little Gluttons are fun, and what they like is to eat, they always eat. But there are a few rules in the world of the Little Gluttons: 1. A Blue glutton eats only Yellow gluttons. 2. A Green glutton eats only Blue gluttons. 3. A Red glutton eats only Green gluttons. 4. A Purple glutton eats Yellow, Blue, Green and Red gluttons. 5. A Grey glutton doesn't eat at all.