A siege battalion trooper.
A Siege Battalion Trooper is a minifigure based the 442nd Siege Battalion from Revenge of the Sith. These troopers were never actually seen in the movie and are basically Clone Troopers in Phase II armor with the same armor pattern as the 212th Attack Battalion and with green markings.
Role in Lego® Star Wars
The Siege Battalion troopers only appears in one set, a set called Wookiee Catamaran, which was released in 2005. In the set, the troopers came with the old type of blasters, with tranparent blue tips. The minifigure had the same legs, torso, and head as normal Phase II armour Clone troopers, except that it had green markings printed on the helmet, and on the torso. These minifigures made an appearance in two of the Lego® Star Wars video games.