Black and White.

When the plane is at a distance from you, the cones in your eyes, which are sensitive to color, are not a effective as the Rods, which are sensitive to black and white. Therefore, you should be concerned not with a specific color, but with the size and type of pattern on the plane. The pattern needs to be easily differentiated between top and bottom, front and back. Thats why you see lots of broad stripes, sunbursts, and checkerboard patterns. These shapes can be easily distiguished. For example, if you use a Sunburst on top, go with a solid color or a single wide stripe on the bottom.

Also consider the background you'll be flying against, particularly on landing. If you have trees behind the plane (green), use a light color on the leading edge of the wing so you'll be able to easily determine attitude.

Planes with a lot of white disappear quickly in a cloudless sky.

Good luck.

Brad