I painted the back of the clear parts.

I struggled to decide what color to use, and I'll post the results of my experimentation.

After looking at the work of others, it seemed that white was the best color for the back of clear parts, but I was curious to see how it would actually turn out on the real thing, so I tried it on the edges of the runners.

1. Gundam Marker Shine Silver
2. Gundam Marker Plated Silver

RG Unicorn Gundam P Psycho Frame Underside Painting | YOU's Gunpla works