Force lightning was a well-known Force ability used to blast dangerous electrical bolts, most often by practitioners of the dark side of the Force, especially the Sith. The ability was commonly referred to as Sith lightning due to the affiliations of its typical users and manipulation of lightning.
Palpatine actually had purple/blue lightning. In Star Wars there are three forms of lightning, blue, purple, and red. In that order is the strength of the different lightning's. Blue being the weakest and red being the strongest.
The most common variation of Force lightning is a blueish-purple color. It was the original version that the Emperor used in Return of the Jedi, and it has continued as the mainstay for most Dark Side users. As such, it has been seen many times on the big screen.
Some have even speculated Sith can grow addicted to Force lightning. This naturally explains why Jedi do not generate Force lightning. Jedi seek to master their emotions rather than be mastered by them; Force lightning is therefore forbidden, as it is best understood as a spontaneous outpouring of hatred and rage.
ALL Force Lightning Colours and Meanings - Star Wars Explained
What does red Force lightning mean?
However, there is a third variety seen only by the most dangerous masters of the Dark Side: Red Force Lightning. Unlike normal Force Lightning, Red Lightning was generated by a Dark Side individual gathering and releasing cosmic energy of the universe itself. It can also be used to suck the life out of a target.
Force Lightning, associated with the Dark Side, can torture, disfigure, and even kill victims through the conjurer's hands with feelings of hatred. Blue Force Lightning is commonly used by villains like Emperor Palpatine and Count Dooku, but Jedi like Rey have also displayed this power.
Either way, while Vader can use most other Force abilities, Force Lightning needs to be channeled, and Vader's limbs are explicitly not connected to the Force. The Star Wars: Episode III - Revenge of the Sith Visual Dictionary confirms Darth Vader cannot use Force Lightning, and even suggests this is the reason why.
The color of the bolt depends on how hot it is; the hotter the lightning, the closer the color will be to the end of the spectrum. The color spectrum in this case start with infared which is red and the coolest up to ultraviolet which appears violet and is the hottest.
Given Rey's lineage as Palpatine's granddaughter, it is also reasonable to assume she is already better attuned to using Force Lightning than the average Force user, with Ben telling Rey that she has all of Palpatine's power within her at the beginning of The Rise of Skywalker.
Mace Windu, with his lightsaber combat form Vaapad, could reflect the lightning back to its source with a "superconducting loop". It required tremendous effort on the reflector's part, however, as seen in Windu's battle with Palpatine; Windu was seemingly able to overcome Palpatine's 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, Count Dooku/Darth Tyranus, Supreme Leader Snoke, and Rey.
During The Rise of Skywalker, Ray accidentally uses Force lightning on the planet Pasana, believing she accidentally killed Chewbacca. While this moment was used to hint at her Palpatine heritage, it also shows that anyone can use the lightning, but only if they channel their anger.
While he never showed the ability to use Force lightning before, it's appearance here helps communicate Kylo Ren's shift in his allegiance, and it's presently the only canon instance of Kylo using such an ability.
Despite this, some Jedi have been known to use their own variations of the ability, either by manipulating the course of natural lightning or by conjuring lightning through the Force instead of its dark side.
Traditionally, yellow lightsabers are associated with Jedi Sentinels, who balance their combat skills with a strong focus on exploration and practical application of the Force. This choice reflects Rey's well-rounded training and her determination to maintain balance in the Force.
After his reincarnation, Darth Sidious aka Palpatine used a blue-bladed lightsaber when he fought Luke onboard his Super Star Destroyer Eclipse. Ultimately, Sith who wielded colors other than red were usually looking to disguise their dark affiliations.
The crossguard blades allow Ren's saber to operate safely – his weapon is constructed around a dangerously flawed kyber crystal, which would be overloaded if not for the lateral plasma vents that create the quillons.
