I have never had trouble seeing my white (slope glider) Zero. I've taken it up so high that it took over 3 minutes to glide back down to terra firma. I will admit to having 20/15 vision in both eyes (used to be 20/10, so I guess age is catching up with me) -- so I'm sure I have an advantage in that regard.
One thing that IS interesting though -- a white airplane against a blue sky is very easy to see. Just don't fly it into a cloud!
Hey! Your Zero looks great! I wish I had taken the time to do all the detail like you did. Watch the CG -- mine is at 42 mm, and STILL climbs at any throttle and neutral elevator! I did not perform the wing incidence modification.