Initially given a blue color scheme, the TIE fighter models for the first film were grey to better film against a bluescreen; TIE fighters in The Empire Strikes Back (1980) and Return of the Jedi (1983) shifted back to being a muted blue. Sound designer Ben Burtt created the distinctive TIE fighter sound effect by combining an elephant call with a car driving on wet pavement. In the book The Sounds of Star Wars, the engine roar is likened to German Junker Ju 87 "Stuka" bombers, who used sirens to frighten civilians on raids. This could have been a possible inspiration for the sound. Combat scenes between TIE fighters and the Millennium Falcon and Rebel Alliance X-wing fighters in Star Wars were meant to be reminiscent of World War II dogfight footage; editors used World War II air combat clips as placeholders while Industrial Light & Magic completed the movie's special effects. Darth Vader's distinct TIE Advanced x1 in Star Wars was designed to make it instantly recognizable, and the TIE Interceptors developed for Sith were designed to look fast, deadly, sleek and frightening.