Onion Skin Problem

Hello (I am new). For some reason I cannot figure out, the onion skin program on my Toon Boom Studio (7.1) which I recently installed is not working correctly. Basically, the previous and the next drawing both are not color coded and are black just like the current frame. Further, I checked the Preferences to make sure, but no matter what I check or uncheck, the color will not turn on.
Does anyone else have this problem or know the solution?
Thank you.

If you are on a Windows based system, try disabling the Aero Desktop Theme by right-clicking the desktop; selecting “Personalize” and choosing one of the basic and high-contrast themes instead.

Also try swotching between Direct3D and OpenGL in the preferences of Studio (close and re-open the software after making the change).