Lightsaber colour has nothing to do with how good you are. Lightsaber colours have nothing to do with anything (as REX said) other then being the users personal choice. Mace simply found a purple lightsaber crystal and put it in his saber, giving him a purple lightsaber.
Oh and Mace is not stronger then Yoda.
Here are the questions that should be asked. I will also answer them.
Who has the greatest strength in the force?: Yoda
Who has the most knowledge about the force?: Yoda
Who is the best swordsman?: Mace.
Who would win in a fight? Yoda, but he would have show off some of that force talent. lol
Also as for lightsaber blade colors.
Sith: Are only allowed to have red bladed lightsabers. As for Anakin not switching over to it in episode 3. Well he was in a hurry and did not have time to make a new one and seeing as Palpatine lost one of his out the Window he is down to one.
Jedi (Obi-Wan's Time): Are only allowed green and blue blades. On rare occasions Purple is allowed.
Jedi (Luke's Jedi Order): Any blade color is allowed.
Dark Jedi: Dark Jedi will use blades of any color.
i know that the color does not effect how good or evil someone is i was just referring to a few things i have read and due to the fact that mace is a good Jedi that uses a light saber technique that is very close to the dark side he might have used a purple light saber to display his proximity to the dark side
Form VII Juyo / Vaapad - Named after the multi tailed, lightning fast Vaapad of Sarapin. It is the hardest to learn and most dangerous form, overwhelming and unpredictable. Closely associated with the dark side. Known users are: Mace Windu, Depa Billaba, Sora Bulq, Darth Maul, Quinlan Vos (incomplete training), Darth Sidious and General Grievous.
and that is the form that i was speaking of so that you don't think that i was lie to cover my tracks and such
Originally posted by Darth Zahanna
Form VII Juyo / Vaapad - Named after the multi tailed, lightning fast Vaapad of Sarapin. It is the hardest to learn and most dangerous form, overwhelming and unpredictable. Closely associated with the dark side. Known users are: Mace Windu, Depa Billaba, Sora Bulq, Darth Maul, Quinlan Vos (incomplete training), Darth Sidious and General Grievous.and that is the form that i was speaking of so that you don't think that i was lie to cover my tracks and such
Nice desciption but here is one i got from theforce.net
Vaapad
this lightsaber combat was developed by Mace Windu, with the assistance of Sora Bulq, during the years leading up to the Clone Wars. It was an aggressive collection of maneuvers, and was considered to be part of the Form VII category. As such, the Vaapad training was considered extremely close to the Dark Side of the Force, and was forbidden to all but the most skilled of Jedi Masters. To Master Windu and his apprentice, Depa Billaba, Vaapad was more than a combat style; it was a state of mind in which the fighter opened themselves so fully to the Force to fight their opponent that they drew power from both the light and dark sides of the Force. The style was named for vaapad creature found on Sarapin. It was all but abandoned after Sora Bulq was consumed by the art in what became known as the blood fever, and himself abandoned the Jedi Order. Master Windu later explained to Obi-Wan Kenobi that Vaapad had originally been created as a way for him to channel his own darkness into a weapon of the light. While this was an adaptation to weakness within Master Windu, it was a potential danger for those Jedi who were unable to control the Dark Side of the Force.
(J1, NEGC, SHPT, E3N)
Originally posted by Jam-Jul_Lison
Also as for lightsaber blade colors.Sith: Are only allowed to have red bladed lightsabers. As for Anakin not switching over to it in episode 3. Well he was in a hurry and did not have time to make a new one and seeing as Palpatine lost one of his out the Window he is down to one.
Jedi (Obi-Wan's Time): Are only allowed green and blue blades. On rare occasions Purple is allowed.
Jedi (Luke's Jedi Order): Any blade color is allowed.
Dark Jedi: Dark Jedi will use blades of any color.
Go to wiki and read up on mace that is where you will get all the info that i stated above and if that doesn't please you then let it go and complain to someone else how light sabers don't determine what kinda Jedi you are and as i said before i never said that the color determines what type of Jedi someone is it just is a choice but i gave a reason to why he might have chosen purple as in mace not Jackson.
Here is some accurate info on the lightsaber. enjoy.
http://www.theforce.net/swenc/newdescr.asp?search=14943&tab=d