While the Signal Flare has many uses, its main purpose is long distance communication. The Garrison uses it as a way to inform the higher-ranking officers how their mission is going while the Survey Corps uses it as a way to communicate (often in the presence of Titans) to the rest of the legion.
The ammo used depends on the mission at hand. The ammo the Garrison uses is the following:
- Green - Mission started.
- Red - Mission failed.
- Yellow - Mission successful.
The ammo the Survey Corps uses for their expeditions beyond the Walls is the following:
- Red - Titan spotted.
- Black - Deviant Type Titan spotted.
- Purple - An emergency of some kind.
- Blue - An order to retreat.
- Green - Change direction of the formation: Fired by the commander in one direction to indicate a change in the direction, and then repeated by the relay soldiers.
- Yellow - This lets everyone know that the mission has been terminated, be it successfully or failed.