Hello Bob! First go to settings by clicking on the menu bar. Next, look at the bottom left and you will see an option called "Extensions & Themes". Click that. Finally scroll down until you find a theme called "Light". Click that. There will be an enable button. Click that and now your browser looks White again. Hope that helps!

It is possible you selected one of the new Colorways themes that are included in Firefox. You can find the built-in themes (light, dark, system) and further down the Colorways themes included in Firefox on the "Add-ons and Themes" page (Ctrl+Shift+A; Themes tab).

• https://support.mozilla.org/en-US/kb/use-themes-change-look-of-firefox
• https://support.mozilla.org/en-US/kb/personalize-firefox-colorways