The Mimban Stormtrooper has the exact same pieces as the Stormtrooper, just with different colors. The print is exactly the same, but the armor is gray instead of white and there are splotches of dark gray and light brown all over the armor. The minifigure also has a cape.
The wet-weather gear stormtrooper, also called the Mimban Stormtrooper, was a variant of the Galactic Empire's standard stormtrooper. Some were part of the 224th Imperial Armored Division on Mimban, a mining planet located in the Expansion Region. Owing to the planet's swampy environment, their armor was heavily customized to allow for optimal operation. Compared to standard stormtrooper armor, theirs had additional space between plates at the shoulders, hips, and knees, allowing a greater range of movement.
Wet-weather gear stormtroopers were armed with E-11 blaster rifles, and some were equipped with bandoliers. They wore waterproof capes, which were necessary for wading through the swamplands of Mimban during the Mimban campaign.