Firefox RICCHIONE

Contents

  1. Peto
  2. Colon

Peto

Type about:config in the URL bar
Search toolkit.legacyUserProfileCustomizations.stylesheets and double-click the field to set it to true

Colon

In about:config, change browser.display.background_color to the color of your choice, head to Firefox’s profile folder by finding it in about:profiles under “Root Directory”, go to the chrome subfolder, open/create userChrome.css and append the following CSS (replacing #1D1B19 by the color of your choice):
        
#browser vbox#appcontent tabbrowser, #content, #tabbrowser-tabpanels, 
browser[type=content-primary],browser[type=content] > html {
    background: #1D1B19 !important
}