Change preview window's background color?

Principle Version: 5.9
macOS Version: latest
Sketch Version: 57.1
Description of what you need help with: Most of my UX elements are black, so I can’t preview any of my components untilI click out to the main window. Can I change the background color? At least to white?

Steps to reproduce the behavior:

Screenshots/Sketch File/Principle file: (if applicable)