Jester is/was a Standard Clone Trooper who was assigned to Slick's squad for the 212th Attack Battalion.Very little is known about Jester, and he only appeared on-screen in the Clone Wars episode "Hidden Enemy", when him and the rest of his squad were on Christophsis battling and being interrogated.
Jester has Standard Phase 1 Clone Trooper armor, while his facial appearance consists of having a "high-fade" haircut with unique trimmed side-burns and a small "stash" of facial hair (to distinguish himself from the other standard Clones.)
Jester is one of the very first Clones to have sideburns and a small "stash". (Other than Punch.)
He looks very much like Punch, who was one of his partners.
Star Wars: The Clone Wars "Hidden Enemy"
Star Wars: The Clone Wars Character Encyclopedia
Star Wars: The Clone Wars "Shadowed" web-comic