Well, I don't know about colourful windows though it works on tabs. Give these a try-

• https://addons.mozilla.org/en-US/firefox/addon/colorfultabs/
• https://addons.mozilla.org/en-US/firefox/addon/tabcolors/
• https://addons.mozilla.org/en-US/firefox/addon/vivaldifox/

Those seem to be great options for TABS, especially if someone wants to use an add-on that "stacks" tabs (one behind another) rather than showing them side by side.

The problem is that TABS (unlike multiple open WINDOWS in Firefox) don't show up in Windows Task manager.

I'm attaching an example of what I mean by "multiple WINDOWS."

Thanks so much for trying to help!

I resized the image I added to provide more contrast with a white background.

I hope this will show what my insane screen looks like (all those open windows!) It would be great if they could display in different colors.

Thanks again for trying to help and to anyone who knows a way to do this.

It can be done but would need to learn some code and search for it as 235million ways or more can customize Firefox now. USSER CHROME URL'S

• https://www.howtogeek.com/334716/how-to-customize-firefoxs-user-interface-with-userchrome.css/
• http://techdows.com/2017/09/classic-theme-restorer-userchrome-css-modify-firefox-57-photon-ui.html
• https://github.com/Aris-t2/CustomCSSforFx/issues/1
• https://www.accessfirefox.org/Theme-Font-Size-Changer.php
• https://www.userchrome.org/
• https://www.accessfirefox.org/Firefox_Accessibility_Themes.php
• https://www.userchrome.org/what-is-userchrome-css.html
• http://kb.mozillazine.org/UserChrome.css
• https://github.com/axydavid/FirefoxUI/blob/master/README.md
• https://github.com/wilfredwee/photon-australis
• https://www.reddit.com/r/FirefoxCSS/

Note not all code is in any one place. Note if have questions on using, please read. If need help with some code it is possible but is not a high priority to get to personal customization with code and only a few here know anything. Patience if ask please.

Please let us know if this solved your issue or if need further assistance.

AlwaysLearningFirefox said

I usually have many Firefox windows open at a time (so that I can also use Windows Task Manager to switch between open Firefox Windows, troubleshoot, etc.).

The Task Manager called up by Ctrl+Shift+Esc?

As you know, there are lots of toolbar area background theme in solid colors, patterns, art, and photos on the Add-ons site. I thought I saw someone say they were showing different themes in different windows using either an add-on or custom style rules. I can see how to change the image using a custom style rule (with difficulty), but I don't understand how to get a different one for each window. The only way I could picture doing it is based on part of the title of a page you're viewing, which wouldn't be very practical.

Thanks, Pkshadow, for the links. Unfortunately, learning code isn't an option for me. I will check those links, though!

jscher2000 said

As you know, there are lots of toolbar area background theme in solid colors, patterns, art, and photos on the Add-ons site. I thought I saw someone say they were showing different themes in different windows using either an add-on or custom style rules.

Now, THAT is news to me, since I use a plain version of Firefox. I wonder what background themes that person was talking about? (For me, "custom style rules" are beyond my tech ability to understand or implement.)

I MIGHT be able to use a theme, though, if one like that was available and could easily be installed. Anybody know of one?

Thanks again, to all!

These are the background themes, zillions of them: https://addons.mozilla.org/firefox/themes/