A yellow-purist is a fighter who specializes in yellow stance and uses it nearly exclusively. In Jedi Knight II: Jedi Outcast and early in the life of Jedi Knight: Jedi Academy, yellow purists were fairly common. Today, most yellow-purists are european members of the Jedi Academy where older purist instructors have passed on their style to newer students. Purists outside of the Academy are very rare. However, yellow-purists are coming back in numbers because of the popularity of the JA+ mod's modified damage system called "multi-player damages". MP damages give yellow stance a significant advantage. Some of the Academy's best fighters are yellow-purists, but competitive JKA hasn't featured a leading yellow-purist in years.
Breaking Down The Style
Because of the nature of yellow stance, yellow-purists are forced to be excellent in movement. It is considered by many experienced players that yellow-purists aren't actually students of the saber nearly as much as they are students of movement. They also typically stay on the ground and rarely do offensive aerials or counter aerials. Nearly all yellow-purists rely on a style that is defensive in nature and is heavily counter based. A lot of emphasis is put on manipulation both with the saber and movement to provoke the opponent into making a tatical mistake. Advanced yellow-purists will put a lot of practice into understanding how saber collisions work in JK:JA and attempt to utilize parries.