1. Install Stylish and restart Firefox when prompted.
   • https://addons.mozilla.org/firefox/addon/stylish/
2. Click the ≡ Menu Button and choose Add-ons.
3. In the Add-ons Manager, click User Styles on the left.
4. Click the Write New Style button at the top. Paste the following in the text box, give the style a name, then click the Save button.

@namespace url(http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul);

.tabbrowser-tab .tab-label { color: black !important; }

If you don't want to install an add-on, you can use the userChrome.css file instead, but I don't recommend it.

• http://kb.mozillazine.org/UserChrome.css

Perfect! That sorted it out. Thank you so much!

Why would you not recommend using the userChrome.css file? And if I wanted to do that, how would I do it?

You can also look at the Classic Theme Restorer extension.

• Classic Theme Restorer: https://addons.mozilla.org/firefox/addon/classicthemerestorer/

• You can find the settings of the CTR extension via its Options/Preferences button on the "Firefox/Tools > Add-ons > Extensions" page.
• You can find extra toolbar buttons and more toolbar settings in Customize (3-bar Firefox menu button > Customize)

See also:

• https://support.mozilla.org/kb/how-to-make-new-firefox-look-like-old-firefox

• https://support.mozilla.org/kb/common-questions-after-updating-to-new-firefox
• https://support.mozilla.org/kb/learn-more-about-the-design-of-new-firefox

pinkpeonies wrote:

Perfect! That sorted it out. Thank you so much! 

You're welcome.

rosawood wrote:

Why would you not recommend using the userChrome.css file?

• Users have to find their profile folder, then create a subfolder in it.
• The file must be created manually. The file name is case-sensitive. Windows doesn't display file extensions by default, which makes it likely that the file will end up named .css.txt which is incorrect.
• Firefox must be restarted for the changes to take effect.
• All styles are lumped together in one file, while Stylish allows separating and toggling styles on and off on-the-fly.

rosawood wrote:

And if I wanted to do that, how would I do it? 

That's explained in the article I linked to. Simpler directions:

1. Copy the CSS code to the clipboard.
2. Start a text editor like Notepad and paste the clipboard contents in a new file.
3. Save the file as "userChrome.css" on your desktop — put exactly that in the save dialog box, including the quotes.
4. In Firefox, type about:support into the address bar and press Enter.
5. Click the Show Folder button.
6. In the Windows Explorer window that opened, create a new folder called chrome
7. Move the userChrome.css file from the desktop into the chrome folder.

• If you want to add additional styles to an existing userChrome.css file, paste the code at the bottom of the file and make sure the @namespace line appears only once at the top.

Note that you can use @import url(); lines in the userChrome.css file to use separate .css files each with their own set of style rules.

These @import rules need to appear before the @namespace line in the userChrome.css file and each of those separate .css files need to have their own @namespace line at the start of the file.

That is what I use to make it easier to maintain changes between various Firefox development builds or quickly disable a specific rule set.

A much easier way to to do this is to install the Tab Mix Plus extension for Firefox. It not only lets you specify any tab text and/or background colors you want (from an easy, intuitive color-picker), but gives you all kinds of control over how your tabs and tab menus behave. It's great!