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> The Avada Kedavra curse is recognisable by the flash of *green* light and the rushing noise emitted from the caster's wand.  
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>  - [*Harry Potter wiki*, *Killing Curse* article, *Nature* Section](http://harrypotter.wikia.com/wiki/Killing_Curse#Nature)
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I thought green was commonly one of the colors used by light side (the good side). Like in *Star Wars*, where Jedi light sabers are green or blue, but Sith light sabers are mostly red. But in *Harry Potter* the light emitted after casting the Killing Curse is green and the defensive spell (casted by Harry Potter) is red. Why the colors are switched in *Harry Potter*?