Clone trooper film series and in the "Star Wars" expanded universe media, a number of specialized trooper units are seen, including elite special forces units such as the 'Advanced Reconnaissance Commandos' (ARC troopers), and Null ARCs, who usually work alone. All clone commandos and ARCs were trained by Mandalorian mercenaries; the elite Clone Troopers are known as Shadow Troopers. The style and color of a clone troopers armor often varies depending on their rank, specialization, unit, or environment, for example, the clone troopers on Kashyyyk wear camouflage green scout-style armour whereas the 501st legion wears standard white armor with blue accents. Another
Star Wars: Dark Forces produced Kyle Katarn and Dark Trooper toys, which are among the [[Star Wars expanded universe|"Star Wars" expanded universe]] items to be turned into [[action figure]]s. The Dark Troopers were also included in books and comics. [[William C. Dietz]]'s novelizations of the "Dark Forces" storyline were adapted to full-cast audio dramatizations. LucasArts extended "Dark Forces" with "[[Star Wars Jedi Knight: Dark Forces II]]" in 1997, and later two more sequels. The [[Star Wars: Jedi Knight (series)|"Jedi Knight" series]] continues the story of Kyle Katarn and has been praised for its quality as a whole. In September 2009, "Dark Forces" was re-released