I selected a new 'background' and 'selected' colors in the Edit/Preferences/Preview tab. The colors show up correctly in the dialog.
I click OK to confirm my dialog choice and return to the thumbnail display.
I was expecting the new colors to show up in the main thumbnail display window, but there was no change.
I shut down the restarted the application, but I still get the old default colors, not the new ones I selected.
Where are these new colors used?