To revert theme changes back to the defaults:
- Open Settings > Preferences.
- Select the relevant page you wish to reset.
- Use File > Reset Page To Defaults to reset it.
- Do any other pages, then click OK.
Pages you may want to reset after using themes (depending on what you want to revert):
- Display / Colors and Fonts
- Display / Images
- Display / Options
- Miscellaneous / Sounds
