The Clone Trooper Captain can be easily identified by his unique red markings. This skin is based off of the live-action Phase 1 Clone Trooper armor from Star Wars Episode 2: Attack of the Clones.

"A Clone Captain, also known as clone trooper captain, was a rank held by clone trooper officers in the Galactic Republic's Grand Army who commanded companies of 144 troopers, although this limitation did not apply to every captain. The sixteen captains of a regiment were in turn led by their respective Clone Commander, or in some cases, a Jedi General. Standard Phase I captains wore armor featuring four maroon circles on the left chestplate as well as a stripe of maroon down the length of each arm, vertically up the middle of the helmet and laterally around the visor." - Wookieepedia