I used to use Microsoft Powerpoint to preview a color scheme. After picking your colors, it had an option to display the scheme in grayscale which gives you the best idea of the relative contrast between the selected colors (ie, what you're going to see at a distance or under poor lighting conditions). The greater the contrast, the better the ability to discern the scheme, and thus the orientation, at a distance. For me, dark blue and yellow were always the best (such as ultracote Midnight Blue and Cub Yellow). In addition, any markings like stripes on the bottom of the wing should be as large as possible. A single 15" stripe under each wing and stab is much better than 2 or 3 6" stripes. I would usually do a contrasting stripe of about 40% of the span, leaving 40% of the base color inboard and 20% of the base color outboard. And as mentioned above, the base color on the bottom of the wing should be dark with a lighter (brighter?) contrasting color for the stripe. The sides and top of the fuse should be the lighter of the contrasting colors and any eye candy trim on the fuse should be a relatively small percentage of area. A busy scheme with lots of colors may look good on the ground but is of no value in seeing your plane at distance and usually makes things worse.