What does the purple lightsaber mean?

To this day, there is still debate as to whether or not purple lightsabers have deep meaning in the Star Wars story. This is especially true since it was revealed that Mace Windu only got one purple lightsaber - because Samuel L. Jackson asked for it. Apparently, Jackson just wanted to be able to stand out from the crowd when there are big battle scenes in the films.

History:

What should George Lucas have done? If someone with a wallet that says "Bad Mother*cheer" asks you for such a favor, you'll do it.

 

That being said, of course the filmmakers had to make sense of this decision, or risk angering all their loyal fans. In a word, this is how the Star Wars Expanded Universe explains what's going on with purple lightsabers: duality.

Because purple is a combination of Sith red and Jedi blue, lightsabers of that color are supposed to suggest an equal affinity with both sides of the Force.

 

An example: Windu practiced the seventh form, a rather rare and unpredictable combat technique that draws power from the dark side of the Force, and is therefore more popular with those associated with the dark side. However, he was never tempted to join the dark side.

This theory of what purple lightsabers mean is supported when looking at the other notable characters who used one, both in canon and in the extended universe texts.

 

Notable characters who used the purple lightsaber

Take for example Revan, who started out as a commander of the Galactic Republic during the Mandalorian Wars. It seems he always had the dark side in him, as he was eventually reborn as the Sith Darth Revan, who caused some serious chaos in the Republic.

 

Another notable character who used a purple lightsaber was Mara Jade Skywalker, who was an Empire assassin for Palpatine before realizing the mistakes of his old master and eventually becoming Master Jedi and an essential ally of Luke Skywalker. This is such an important paradigm shift for Mara, as she originally planned to destroy Luke to fulfill Palpatine's last wish, and the duality is aptly reflected in her deep magenta lightsaber.

 

Purple lightsaber reflects the human personality:

More than anyone else in the Star Wars universe, Kyp Durron is the purple lightsaber that best illustrates the duality of the human. He has made significant contributions to both the light and dark sides of the Force. He briefly fell to the dark side in 11 ABY, and is credited with many deaths during his rage against the Imperial Order. While imprisoned in the herb mines, he harbored deep anger and a desire for revenge.

Once released, he was responsible for the destruction of many Imperial targets, even killing his own brother, all under the influence of Exar Kun. However, as the latter's power waned, Kyp managed to escape his trance, becoming Skywalker's most promising apprentice and eventually becoming a pioneering Master in the New Order of Jedi.

 

Aside from their differing allegiances to both sides of the Force, those who use purple lightsabers are seen as reserved, sympathetic and compassionate, but vulnerable to their temperaments. When given the choice, purple swordsmen prefer to operate alone and often find themselves in deep introspection, possibly trying to find their true purpose, despite being drawn to both Light and Darkness.