Corsaire, Uwe and I had similar flare signals in online co-ops.

White = Leader only: Start signal / also Landing signal / also "attack designated target"

Red = Immediate danger (usually enemy aircraft at strike range overhead)

Green = Leader: Re-assemble here; wingman: I lost contact (answered with green from leader)

Yellow = I have a problem / I'm wounded - I return to base or put the craft down

In Otto Fuchs' book I read the Germans also had a "multi-stars flare" with many white stars.

Vice-President of the BOC (Barmy OFFers Club)
Member of the 'Albatros Aviators Club' - "We know how to die with Style!"