Hi, if you mean the Firefox UI toolbars, open the 3-bar menu > Customize, then Themes (at the bottom of the window) and select 'Light' then click Done to save. There is also a large number of other themes here: https://addons.mozilla.org/firefox/themes/ If you want to make your own theme, see: https://addons.mozilla.org/firefox/addon/firefox-color/ If you want to change website colours, see: [[Change the fonts and colors websites use]] ''If your question is resolved by this or another answer, please help other users by marking the best reply as Solved. Thank you!''