One factor to remember is that the human eye loses color definition before it loses shade definition.

By that I mean as the model goes away, we lose the ability to see colors (it looks like shades of grey from a distance) before we lose the ability to differentiate the shades.

So, it's no use trying to differentiate top and bottom with, say, red against blue, as they look the same when we lose the color definition, which happens quite quickly.

I always put contrasting stripes fore and aft on the bottom, and stripes across the span on the top. That way you have a chance of knowing whether its inverted or not!

-David C.