The Origin Of Luke Skywalker's Green Lightsaber Came From A Return Of The Jedi VFX Problem
The lightsaber is one of the most recognizable and iconic parts of "Star Wars," a veritable symbol for the media series' legacy. There's perhaps no better proof that George Lucas was looking to make an epic science-fiction fantasy (emphasis on the "fantasy") than the Jedi Order's medieval-like plasma sword weapons. The lore behind the lightsaber is expansive and any dedicated "Star Wars" geek will mention that the colors symbolize rank and personality. The honest truth, though, is that the different colors were originally the result of special effects decisions.
It was pretty easy to distinguish the good guys from the bad guys in the original "Star Wars" trilogy. The Jedi wielded blue lightsabers while Darth Vader repped his Sith loyalties with a glaring red blade. After Luke loses his hand along with his lightsaber in "The Empire Strikes Back," he changes his color preference in "Return of the Jedi," reappearing with a green blade. According to the lore, much of which is part of the no-longer-canon "Knights of the Old Republic" video games, the color blue denotes the physicality of a Jedi Guardian class, green symbolizes the more Force-oriented Jedi Consular, and yellow was the choice of the balanced Jedi Sentinel. These, of course, were the result of an RPG class system, and the real story behind the lightsabers is more about visual consistency than mythology.
Green against blue
Luke's lightsaber was originally blue in the "Return of the Jedi" promotional material to reflect the hue in the previous films. As Lucasfilm creative executive Pablo Hidalgo explained to Vanity Fair, "In that universe, at that time, as far as anyone knew, lightsabers were red or they were blue." However, green made for a more striking visual contrast between Tatooine's blue sky and yellow sand. Besides, Luke lost his original lightsaber, so the switch worked. Hidalgo pointed out that "as much as we like to mythologize why it's green and what that all signifies, sometimes there are very pragmatic filmmaking reasons behind these things."
For instance, Mace Windu's purple lightsaber in the prequel trilogy was all because Samuel L. Jackson wanted it that way in order to stand out more, despite fans claiming that it's because he's dabbled in the Dark Side of the Force. There are also some canon works that have hinted at symbolic meanings behind the lightsaber colors. The Jedi Temple guards in the animated "Star Wars: The Clone Wars" series, for example, wield yellow blades, the same color as Rey's lightsaber seen at the end of "The Rise of Skywalker." That might denote its users' roles as guardians and protectors of the Order. In addition, the Darksaber in "The Mandalorian" series has a whole Excalibur-like backstory behind it.
Then again, these do look pretty cool, so who's to say what's behind a deeper meaning?