but didn't the torches move out when they had the sort of starfish shaped formation and they were all yellow? seems hard to believe they would've been able to coordinate the extras moving far away and then moving right back in position.

What about something low tech like: the field has a grid with infrared emitters pointing up spaced let's say 6 feet apart, when changing positions extras have to keep the torch vertically for a second for it to receive its id from the local emitter, then you simply broadcast every instruction to everybody and each light knows to look only for instructions for its id

As long as you are ok with setting up the emitters on the ground and the assumption that you can "re-sync" the position at every position change, seems like it'd be fairly straightforward