Or dark on bottom, light on top.

But in either case, use light with dark trim and dark with light trim. This is very important. Here's why:

Let's say you pick white, or light blue for the top of your plane. when you bank the plane toward you, it will be very difficult to see against the sky, so a few BOLD stripes in a contrasting color is a very good thing to have.

By the same token, dark colors can be lost against a dark background such as a distant line of trees, or a mountain.