Ah yes, the stormtroopers. Now we are their enemy, so kill them if you must. But do not hate them. They are but cloned slaves.
—Shahmzar Aonda-Alci to Gir Kagn
The 31st Legion was a legion in the Grand Army of the Republic and later the Stormtrooper Corps.
It was led by senior clone commander CC-1696 "Bryse", often in conjunction with Jedi General Shahmzar Aonda-Alci. General Aonda-Alci's Padawan, Commander Ac'churo Valnuon, also led the 240th Regiment, a division of the 31st, along with clone trooper commander CC-3839 "Mirshe".
Early during the war, elements of the 31st were under the command of General Echuu Shen-Jon. General Shen-Jon used the legion in the Hunt for the Decimator, which ended in the Battle of Krant. Shahmzar and his Padawan occasionally played minor roles in the campaign as well.

A member of the 31st legion in Phase I clone trooper armor
The troopers of the 31st Legion were distinguished by their cyan-trimmed armor. They were among the first in the army to color their armor according to division rather than the ranks of individual troopers.
Behind the scenes[]
The cyan armor is a fanon retcon of sorts for the team color for Echuu's clone troopers in the Star Wars: Galactic Battlegrounds campaign.