From Halopedia, the Halo wiki
The Promethean Soldier Officer is primarily white in color with red glowing highlights, contrasting the regular unit's silver/grey color palette. Similar color differences are seen within the Knight Commanders. The Soldier Officer also appears slightly larger and taller than the standard Soldier, hence why Soldier Officers are sometimes nicknamed "Big Soldiers".
Soldier Officers are commonly armed with Splinter Turrets.
It is highly recommended to deal with Splinter Turret-wielding Soldier Officers from a safe distance as the Splinter Turret's projectiles are dangerous due to their strong knockback that can easily disrupt a Spartan while they are reviving another Spartan, which can then lead to the entire fireteam dying quickly. Use the scenery and thruster pack boosting to evade the projectiles, seek cover, and then fire away at the Soldier Officer with a precision weapon and/or explosive weapons. Soldier Officers have heavier armor than standard Soldiers, taking up to a full clip of a Boltshot on Heroic or Legendary before their armor breaks.
List of appearances