Fun Fact: Each of the Therian Forms has a gem on their stomach that matches the typical colors the four cardinal beasts they each represent.
Tornadus' is red, Thundurus' is blue, Enamorous' is green, and I forget what color Landorus is (because when was the last time you saw his stomach), but I believe it's yellow (which is a little off since Byakko is typically white, but I understand why the change was made).