During the Clone Wars, clone trooper lieutenants were clone troopers specially trained as officers on Kamino, and recognized by the blue markings on their helmets and torso. They would however, often wear armor that was specifically painted to match the environment.[1]
Clone trooper lieutenants wore distinguished blue Phase I clone trooper armor during the first years of the Clone Wars; later they wore armor that distinguished them by division and not by rank. ARC trooper lieutenants sported ARC trooper armor, which optionally provided some of these units with additional weaponry, such as hidden flamethrowers. These ARC lieutenants also wore skirt-like kamas that dampened blasts, had rangefinders attached to their helmets, and wore command shoulder pauldrons. However, the markings on the ARC lieutenants' armor remained blue.
Rank
They were a few ranks above a Sergeant and below a Captain. The rank of lieutenant among clones is also used for the ARC trooper private units. They sported additional command, along with better training and varying weapons, including wrist-mounted flamethrowers.