My headcanon is that Mace once got a little carried away during a duel in his younger years, his emotions getting the better of him and this began to “bleed” his then-blue lightsaber. But he began to see the error of his ways and carries this lightsaber as a reminder of the fragile balance between light and dark.
Then of course they had to give other Jedi purple lightsabers and mess this up.
He studied a style that is a bit closer to the dark side so that he can channel the emotions of a dark side user against them. This was why he was able to defeat Palpatine pretty easily while his support were finished quickly and even Yoda was only able to fight him to a draw. Windu was a hard counter for Palpatine.
So your headcanon wasn’t completely off vs what was in the EU.
My headcanon is that Mace once got a little carried away during a duel in his younger years, his emotions getting the better of him and this began to “bleed” his then-blue lightsaber. But he began to see the error of his ways and carries this lightsaber as a reminder of the fragile balance between light and dark.
Then of course they had to give other Jedi purple lightsabers and mess this up.
He studied a style that is a bit closer to the dark side so that he can channel the emotions of a dark side user against them. This was why he was able to defeat Palpatine pretty easily while his support were finished quickly and even Yoda was only able to fight him to a draw. Windu was a hard counter for Palpatine.
So your headcanon wasn’t completely off vs what was in the EU.