Windows 10 Operating System _ Change default TAB color from white to RED COLOR or make it more CONSPICUOUS when using Firefox Browser

Hi Copilot , I have a question for you and I hope you can really help me with this problem. I am running a Firefox browser on my LInux UBUNTU 25 Operating System and I have the habit of opening so many TABS on my Firefox Browser . Sometimes I open up about 20 TABS with 20 different websites and sometimes I open up about 10 TABS with 10 different websites . When I move from one TAB to another TAB or from one website to another website quickly , I CANNOT SEE THE TAB MOVEMENT clearly because the TAB is white color ! Copilot , is there any way I can change the default color of the TAB to RED COLOR so that it is more conspicuous so that when I move from one TAB to another TAB in order to move from one website to another website quickly , I CAN SEE THE TAB MOVEMENT CLEARLY ? Copilot , is it very difficult to do this ? Copilot , if possible I would like you to be able to do this on my Windows 10 PC/Desktop , too , and I hope you could help me on this , too ? THANKS Copilot.

 

MICROSOFT Copilot Answer 

Great question! You’re absolutely right — Firefox’s default tab colors can be hard to distinguish when you’re juggling 10–20 tabs. The good news is that you can customize tab colors in Firefox on both Linux (Ubuntu) and Windows 10, though it requires a bit of tweaking.

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🎨 Option 1: Use Firefox Themes (Easy)

• Firefox supports themes that change the look of tabs, toolbars, and menus.
• You can install a theme that makes active tabs red or more visible.
• Steps:
  1. Open Firefox.
  2. Go to Menu → Add-ons and themes → Themes.
  3. Search for “red tab” or “high contrast tab” themes.
  4. Install and apply the one you like.

This is the simplest way, but themes may not give you exactly red tabs unless someone has created one.

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🛠️ Option 2: Custom CSS (Advanced but Powerful)

Firefox allows deep customization using a file called userChrome.css. With this, you can force tabs to be red.

Steps (Linux Ubuntu & Windows 10 are the same):

1. In Firefox, type about:config in the address bar.
2. Search for toolkit.legacyUserProfileCustomizations.stylesheets and set it to true.
3. Find your Firefox profile folder:
   • On Linux: ~/.mozilla/firefox/xxxx.default-release/
   • On Windows: C:\Users\<YourName>\AppData\Roaming\Mozilla\Firefox\Profiles\xxxx.default-release\
4. Inside that folder, create a folder named chrome.
5. Inside chrome, create a file called userChrome.css.
6. Add this code:

/* Make active tab background red */
.tabbrowser-tab[selected="true"] {
    background-color: red !important;
    color: white !important;
}

/* Make inactive tabs more visible */
.tabbrowser-tab {
    background-color: #ffcccc !important;
    color: black !important;
}

7. Restart Firefox. Your active tab should now be bright red, and inactive tabs will be light red.

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⚡ Difficulty Level

• Themes: Very easy, no coding needed.
• CSS method: Slightly technical, but once set up, it works beautifully on both Ubuntu and Windows 10.

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✅ Recommendation

If you want a quick fix, try themes first. If you want full control (like making tabs red, green, or even rainbow-colored), go with the userChrome.css method.

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Would you like me to prepare a ready-to-use userChrome.css file for you with red active tabs and maybe a softer color for inactive tabs, so you can just drop it into your Firefox profile folder?