How are Christmas Light Shows made?

In terms of light shows that feature flashing lights, regular Christmas lights are installed in the desired pattern. Then, separate blinking light bulbs are added. You can tell they are different because the tip of the glass bulb is painted red or silver to indicate it is the bulb that will turn on the string's ability to blink. It takes a bit of trial and error once the lights are all sufficiently warm, but many of these light shows are coordinated with computers to run on a timer. That is how the bigger shows (i.e. Walt Disney World) look the way they do.