Hi Johns, you would need a type of paint that would not harm the phone but an idea just popped into my head. If you have a good Hobby shop in your area you might look there and see if they have Top Flite Monokote trim sheets. I would get one of the neon colors and cut out the shape you need and stick it to your wing. I do this with balsa wood airplanes as it helps to tell if I'm right side up when flying!
Michael Johnston