Corrected entry: At the end of the movie when everyone is waving to the Ghostbusters and Ray is backing up the car, on the light bar on Ecto 1, the outer lens is a solid blue light bar. When the car goes to drive away, it's a clear light bar with blue lens covers over each individual rotator.
lbfire20
4th Nov 2009
Correction: The light bars on the front and back of the roof of Ecto-1 are blue but have a solid white colored portion in the center, and nothing about them changes in between shots.