It's a little confusing sometimes which colors are picked up from your Windows theme and which are set by your Firefox theme. (1) If you like your current Firefox theme, you could try this add-on to tweak it: [https://addons.mozilla.org/en-us/firefox/addon/theme-font-size-changer/ Theme Font & Size Changer]. After installation, a new "A" icon should appear at the end of the Navigation toolbar. Click that and change Color (for text) or Background Color (for the background) from Normal to something easier to read on a dark background. Does that work? Since you probably won't need this button very often, you can drag it off the bar using the Customize feature. To call that up, you can either: * right-click a blank area of the tab bar > Customize * View menu > Toolbars > Customize Drag and drop the button with the others in the dialog, then click Done. (2) If you think you might like to experiment with other color combinations, you can check out lightweight themes here: https://addons.mozilla.org/en-US/firefox/themes/ Can you find a good readable combination?