Force lightning has been seen various times through the Darth Vader’s backstory.
Following the acquisition of Lucasfilm by Disney, the studio began working on a sequel trilogy with the purpose of closing the Skywalker saga and introducing new heroes and villains, as were Rey, Finn, Poe Dameron, Kylo Ren, and Supreme Leader Snoke. Each trilogy introduced new powers from both sides of the Force, but there are some that remained the same, as is Force lightning. Although this power is not exclusive to the Sith, as there have been some light-siders who have used it (Rey, for instance), it’s commonly used by those with affinity with the dark side, as it's through this that they can conjure it.
Force lightning is a technique involving a discharge of electrical energy from the conjurer’s hands, and it’s mostly used to torture their target, as it can inflict severe pain and even cause disfigurement. In some cases, as when Palpatine used it on Mace Windu in Star Wars: The Rise of Skywalker. All these examples have shown Force lightning to be blue, but as it turns out, there are three other colors this power can manifest in (without them altering the intensity of the lightning), though not all of them appeared in the Skywalker saga.
Blue-Purple Force Lightning
As mentioned above, the most common color in Force lightning is a blueish-purple tone. In Star Wars canon, this has been used by Darth Sidious, Star Wars: The Last Jedi, with the particularity of projecting it against the floor so it would bounce upward and knock the target off their feet; and Rey summoned this power to rescue Chewbacca, who she believed was trapped in a First Order transport that was leaving Pasaana.
Green Force Lightning
Green Force lightning has been seen in Clone Wars, used by Mother Talzin. This tone of green is like the one of the magical ichor, also known as the Waters of Life or spirit ichor, a luminescent green mist from the depths of Dathomir. The Nightsisters, an all-female order guided by the Mother (a title given to various women, including Talzin), knew how to summon the ichor through their magicks, so with that in mind, it’s not surprising that their Force lightning comes out green instead of the typical blue-purple tone.
Yellow Force Lightning
Another color Force lightning can manifest in is yellow, which has appeared in canon novels within the Star Wars universe. This yellow version was used by Darth Momin, a Sith Lord and dark side scholar who made his debut in the comic book Darth Vader: Dark Lord of the Sith 22. Momin once planned to pour the Force into his engine (a weapon with enough power to obliterate an entire city) at the moment of ignition through Force lightning, shown to be yellow, and with this slow down time and trap the expressions of horror and pain on the city’s inhabitants. Unlike Mother Talzin and the green Force lightning, which color is linked to their magick, there’s no apparent reason for Momin’s lightning to be yellow.
Red Force Lightning
Being a power summoned through the dark side of the Force, it’s not surprising that Force lightning can also manifest in red. This variant was used by the Son, who is the manifestation of the dark side itself. Because of this, the Son possessed a lot of power and was virtually immortal as he could only die after his father’s death. Due to his strong connection to the dark side, his Force lightning was red, a color that appears to only be able to be manifested by the most powerful individuals. In the comic book Darth Vader: Dark Lord of the Sith 25, Vader was able to use red Force lightning when he sent an astral projection of himself to enter a portal in his castle on Mustafar. Vader used it against Palpatine, who was blocking his way as he tried to reach a vision of his wife, Pé Amidala.
It’s unknown if the Star Wars universe will add more colors to Force lightning, especially as in the non-canon side of it there are white and black Force lightning as well, but it wouldn’t be surprising if it does. As for the ones that already exist in canon (aside from the “traditional” blue-purple tone), it’s yet to be seen if their stories will be further explored in other media, or if they will be given different levels of power at some point – after all, the Star Wars universe is always in constant change.
