Emblems
From Halopedia, the Halo wiki
Summary
In Halo 2, when a Character Profile is created, there is an option to make an Emblem for your character. These Emblems are only used in Multiplayer modes and online play. It allows other players to easily identify you in battle. Also, in the gametype "Territories", your emblem appears on a flag inside the area of a territory if you take it, identifying who took it. The color of the emblems depend on primary and secondary colors and the backgrounds are usually determined by the primary and secondary armor colors. On a player model, these emblems are seen glowing on the back and the left and right shoulders
