Cute Or Terrifying

On the face of it this handwritten note on the neighbours window is cute and funny. Pop some movie horror music on it, add a little backstory, and this becomes a terrifying note just before the killings begin again!

Why are hotel neon 'vacancy' signs red?

Shurely they should be green when they have rooms - green for, "Go on, come in, we've spare rooms"! Red for, "Nah mate, full up"