On scheme to avoid is the up-down checkerboard.

By that I mean let's say you decide to make one wing Blue and the other Wing yellow. Very easy to see right? Well, don't make the bottom of the blue wing yellow and vice versa. if you do that you won't know which side is up. Yes, a plane can be inverted and other than the fact it's diving for the ground, it can be hard to tell at even a moderate distance.

For a trainer, all that glinty stuff and stripes don't really help much. I recommend you make one wing a darker color and the other wing a lite color - same color top and bottom.

Problem with stripes and such all over the wings is that it looks like it should be visible but it usually all blends together in the air.

Hope all that made sense. If not just say so and I'll try to explain it better.