The Key word for visibility is "Contrast"

You want a combination of light and dark colors in sections large enough to be seen from a distance.



You also want a good contrast between top and bottom so you can easily tell which side you're looking at.

This is my favorite color scheme. Light on top, Dark on bottom. This allows you to see it well whether you have a light or dark background, or if it's overcast.

and you can easily tell top from bottom