IMO, the "best" visibility trim scheme is a Cub yellow plane with whatever color you like that's dark leading edges on everything and a red fuselage top. Tapering the leading edge dark color to be wider at the wingtips helps too, but I can't explain why. Make the bottom of the wing solid with your dark color and the bottom of the fuselage solid with your light color. That scheme gives you a color contrast against any color sky, and also a distinct shape to see at distance because of the internal contrast on the plane itself. On bright sky days you'll see the dark color at distance, and on darker sky days you'll see the yellow. The Cub yellow as opposed to a lemon yellow is a bit darker and more saturated so it pops against a blue sky better and also will look dark against a white overcast sky.