Sally, if you were a tasty bug and you were hiding in the grass so a bird would not find you and eat you, what color would you like to be?
Sally: "Green!"
Exactly! So if you are a cavity causing germ hiding on a tooth, what color would you be?
Sally: "White?"
Right again! That makes them invisible on your teeth. So when you brush your teeth, how do you know if you got them clean?
Sally, "Hmmm. I don't know. I can't see the germs."
