 The Royal Flying Corps and its successor the Royal Air Force have employed numerous versions of the roundel since then.By 1917, a thin white outline was usually added to the roundel, to make the blue of the outer circle easier to distinguish from the dark camouflage colours produced by the PC.10 or PC.12 protective doping.On squadrons operating at night there was not the same need to make the marking more conspicuous, in fact it became customary to overpaint the white ring of the roundel itself – either in the camouflage finish of the aircraft as a whole, or in red.