RE: Monokote Ultrakote or whateverkote
I like contrast between the top and bottom of the wing. Light on top, dark on the bottom or vice verses. Maybe something solid on the top and stripes on the bottom, doesn't matter, just something different which then indicates the top from the bottom. I've found white undersides to be difficult to see in certain conditions, as is sky blue. However, white or sky blue with a contrasting large area at the tips is good also.
Scale airplanes are basically limited to what the full scale plane is like, from my point of view. Your view may certainly be different!