Or go with the old roadside motel "No Vacancy" sign model. Red neon letters, but the two words are on separate circuits. So you can have "Vacancy" lit when you

Or go with the old roadside motel "No Vacancy" sign model. Red neon letters, but the two words are on separate circuits. So you can have "Vacancy" lit when you have rooms, and then turn on "No" when you are full. Red is also the best color to be readable at a distance, especially at night or in the rain.