What OS are you on? The default style on Windows takes your system title bar color (or a dark blue if you don't have Windows set to show the system accent colo

What OS are you on? The default style on Windows takes your system title bar color (or a dark blue if you don't have Windows set to show the system accent color on title bars); the default style on OSX uses a dark translucent background. Both use light gray tabs and a light gray toolbar background. If you've migrated from a previous version of Firefox and customized the browser at all, you may not be getting the default settings, though-- right-click the toolbar or Bookmarks Bar, and take a look through the options at the bottom of the page. Themes will give you an option between the default, light, and dark themes (it sounds like you're stuck on the light one); density adjusts spacing in the toolbar area. And you can check "Drag Space" to add space above the tab bar for dragging, or check "Title Bar" to turn the system title bar back on.