We've had to learn to be so patient, eh Dantes!

Mogster, those cannisters show the percussion side of individual red, white, and green signal flares, to be fired by the pilot (the flight leader) using his hand-held flare pistol.

Possible signals, differentiated by colors:
"reformate"
warning:"enemy in proximity"
rallying:"joining/combining with friendly formation"
upon landing:"damaged/wounded flight members in-bound"

Here's an example of a German WWI flare pistol:



And a bloody British Webley: