The German Luftstreitkräfte during the First World War rather idiosyncratically permitted its fighter pilots to paint their assigned planes in whatever colour scheme they wished. While the men of the British Royal Flying Corps, by comparison, were stuck with the standard dun-brownish colour, German planes could be anything from pure white to pure black to pink with green diamonds. Blue/white stripe jobs were popular, apparently, as were blue/yellow.

It's not entirely clear to me if this doctrine extended to heavy bombers as well, but a great deal of variety was certainly permitted with fighters. In the case of a pilot like Richtofen, the total lack of camouflage was sort of the point: he wanted his enemies to know he was coming, and to fear the likely consequences.