Method 1 (script):
1. Create a new group,
2. Temporarily move the units to this new group,
3. Set combat mode for the new group,
4. Rejoin units back into their original group.
5. Use the combatMode command on one of those units.
6. It always returns "YELLOW"
Method 2 (engine commanding menus):
1. While being the leader of a group, use the commanding menus to order a certain unit to hold fire.
2. Use the combatMode command on that unit.
3. It always returns "YELLOW"