Oh I think that's absolutely an important consideration, Krokodyl. I'm a fan of orange or yellow for the top with a dark line at the leading edges of the wing and tail, then a dark bottom for the wing and tail and a light colored fuselage. Complimentary colors contrast the best at the longest distances, so yellow and purple and blue and orange are good choices. Red and green or red and blue don't work, because at distance they will turn to the same shade of grey.