Editor:
1. Place an infantry Fire Team, player as leader.
2. Make at least one other unit playable.
Ingame:
3. Assign two men as team red and two other as team green.
4. Switch to the playable character (doesn't matter if with the U key or with the quick menu method).
5. Switch back to the leader.
6. Observe, that everyone is on team white and red:green team assignments are gone.