Kylo Ren's lightsaber was a crossguard lightsaber wielded by Kylo Ren, Supreme Leader of the First Order and master of the Knights of Ren. The lightsaber was previously Ben Solo's lightsaber, constructed by Ren in his life as Ben Solo while training as a Jedi Padawan under his uncle, the Jedi Master Luke Skywalker.
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.
Kylo Ren quite liked the sinister crackle emitted by this distinctive lightsaber but, even though Star Wars sequel viewers never realized it, the use of a damaged kyber crystal potentially granted Kylo Ren's lightsaber unusual Force powers.
Kylo Ren's lightsaber had a cracked kyber crystal, which generated an unstable blade. The excess power was vented out the sides, thus creating a crossguard-like design. The most important and prestigious vessels of the First Order had weapons upgraded with kyber crystals from some secret source in the Unknown Regions.
My opinion is that Kylo wants Anakin's lightsaber just due to the fact, it belonged to Anakin. And also Anakin killed dozens of Jedi during the Sack of the Jedi Temple so it's symbolic as a symbol of the fall of the Jedi, so that could also play a part in it, but since Kylo admires his grandfather so much.
Lightsaber Colors Used to Matter
A brief who's who of users with blue lightsabers includes Obi-Wan Kenobi, Luke Skywalker, Anakin Skywalker (Hayden Christensen, pre-youngling slayer), Shaak Ti, and Count Dooku (Christopher Lee, pre-dark side/ass handed to him by Yoda).
A crystal embodies the Jedi as the heart of the lightsaber, and pure kyber has no color until it's bonded to the Force user. This process likely resulted in Rey Skywalker's lightsaber being yellow.
Any kyber crystal could be bled by a Force user, including one's own, for example, if they were a former light side practitioner and kept their lightsaber.
Black is the rarest lightsaber color in the world of Star Wars. For a while, the only known black lightsaber was the Darksaber, forged a thousand years ago and owned by a Mandalorian Jedi.
Healing Kyber Crystals
While it's possible for the Sith to corrupt Kyber Crystals, it's also possible for the Jedi to restore them. The Chronicles of Brus-bu is one of the ancient Jedi texts that explains how Kyber Crystals can be healed after the Sith completes the bleeding process.
Even though Kylo Ren uses a red lightsaber, harnesses the dark side of the Force, and wears a cape, he is not a Sith. Because of that, he can never hold the title of Darth. Instead, he was just a chaotic mess of the dark side (until he eventually found his way back to the light).
The lightsaber's redesign was a byproduct of the bleeding process that damaged its kyber crystal, rendering it dangerously flawed and unstable, and necessitating the lateral vents were meant to prevent the cracked kyber crystal from overloading.
Description. Leia Organa wielded a blue-color lightsaber during her year of training. Leia Organa's lightsaber was a blue-bladed lightsaber powered by a kyber crystal in the core of the hilt.
We've known for years now that Kylo Ren's lightsaber crackles and sputters the way it does because the kyber crystal that powers its blade is unstable.
As the grandson of Darth Vader and the granddaughter of Darth Sidious respectively, both Ren and Rey formed a prophesied Force dyad. Due to their innate connection, they were able to communicate with each other across light-years.
Gathering his strength, Kylo hurled his Sith lightsaber into the sea. Ben Solo had returned. Ben returned to Exegol, where Rey had confronted Palpatine. She gave him the Skywalker lightsaber, which he used to strike down the Knights of Ren.
When Obi-Wan Kenobi's blue saber clashed against Darth Vader's red in the first film, each color was a representation of their innermost selves, a legend which would take further shape and definition as the saga continued. Originally, it was a pretty simple code to crack. Blue was good. Red was evil.
The weakest and most harmless type of lightsaber is the one that has been “baby-proofed”: the training lightsabers. As the name implies, this type of lightsaber is only utilized in the context of training very young Jedi to one day become Jedi Masters.
During his years as a Jedi, Obi-Wan Kenobi fought with three lightsabers.
It appears rarely in the Star Wars universe—so rarely, in fact, that the current canon recognizes only one carrier of a white lightsaber. Ahsoka Tano, the former Jedi Padawan who aided in the rebellion against the Galactic Empire, is acknowledged as the sole possessor of the white lightsaber.
Construction. In the construction of a Sith lightsaber, individuals partook in a process known as bleeding. By ways of the Force, they would pour negative emotions, such as rage, hate, fear, and pain into kyber crystals. The process would result in the crystals gaining a distinctive crimson or red hue.
So, that's the real reason Anakin's saber didn't change color -- because the process of lightsabers changing colors (after bleeding) didn't exist as a concept when Revenge of the Sith came out. At the end of the film, Darth Vader loses his lightsaber during his duel with Obi-Wan.
The Darksaber goes back to the time of Tarre Vizsla, the first Mandalorian to become a Jedi Knight. He created a one-of-a-kind lightsaber with a flat blade of dark, swirling energy. In the Star Wars Rebels episode “Trials of the Darksaber,” Fenn Rau shared more of the Mandalorian folklore surrounding the weapon.
Silver Lightsabers
In Star Wars: Episode III – Revenge of the Sith, Obi-Wan Kenobi uses a silver lightsaber when he faces off against his former apprentice, Darth Vader. This represents the end of Kenobi's time as a Jedi and the beginning of his new role as a protector of peace.
Without a doubt, the most notable Jedi with a purple saber is Mace Windu, portrayed in the prequel trilogy by Samuel L. Jackson. Audiences first got a glimpse of the unusual blade in Episode II: Attack of the Clones, making Windu the coolest Jedi in one cinematic moment.