[aviatorsneah]

i'd say the bulk of "modern" aircraft during WW2 used nav lights, although obviously not all the time. Green on the right wing tip, red on the left, and sometimes a white on the tail. This is to not only show a position of another aircraft, but more so to see it's orientation (whether its coming to or gowing away from you). Americans used formation lights as well on their aircraft, usually on the underside, that consisted of red, green, and amber lights. The various colors could be turned on for signaling at night while in formation. Not lights, but same idea, I read that the Me262 and later Dora-9s had flare dispensers on the bottom of the fuselage for the same purpose?

heres a description of Nav light usage i made up real quick. This is what you'd see in the darkness: