Ken is right about the wide stripes. 3" minimum. White-Purple, Yellow-Red, Black-white, Green-white, any combo that really contrast to each other. The eye will pick up the difference in contrast much quicker that the difference in color.

White is a susprising good color for long distance visiability. We have a lot of birds around our field, including Sea Gulls, Vultures, and Egretrs, The white ones will show up much quicker that the darker ones. However, when they go silhouette, the color isn't important, but a contrast is.

I have a Pheonix Fun Star that I about lost all three of the first three flights. It was covered in trasparent yellow covering. It turned into a yellow blob as soon as it got within 90 degrees of the sun. After the third flight, I stripped it down and recovered it. The wings are white on top, and big white/turquoise stripes on the bottom The Cowl is red and the fuselage is white with more red/torquoise and yellow stripes to a prominate Torquoise/white combo on the vertical/rudder. One of the guys calls it "Patches", but you don't have trouble seeing it, or telling which direction it is going.

Big and bold color differences may not be the most pleasing to look at, but they come back home in one piece most of the time.

Don