The Com Guards simply paint their vehicles white for official occasions and use appropriate camouflage for combat.
Per FM: ComStar, page 17.
Rifleman, Battle of Tukayyid (p 165)
Sentinel, Battle of Tukayyid (p 178)
The insignia of the Second Army is a Black Knight-class BattleMech, its right arm raised in a salute. Per FM: ComStar, page 22.