I think he is talking about fire teams within a squad.
2,3,4 are team red
5,6,7 are team green
So that, for example, you could start a mission with the player as group leader with one fire team in one position, and another fire team in another position. Placing the units is easy, but how can you start the mission with the colours already assigned to the fire teams?
The default is for the whole group to be in one fire team, team white.