Make sure you haven't enabled High Contrast Mode in the OS settings.

Make sure you allow pages to choose their own colors.

• Settings -> General: Fonts & Colors -> Colors: "Override the colors specified by the page with your selections above"

Try "Never" if the default "Only with High Contrast themes" isn't working.

You can change this pref on the about:config page from 3 to 2 to revert to the Firefox 94 behavior regarding to prefer dark or light background for webpages.

• layout.css.prefers-color-scheme.content-override [dark:0, light:1, system:2, browser:3]

You can open the about:config page via the location/address bar. You can accept the warning and click "I accept the risk!" to continue.

• https://support.mozilla.org/en-US/kb/about-config-editor-firefox

Thanks for the suggestions but it didn't work.

Do you mean the Windows 7 "Aero" style background on the title bar / menu bar / tab bar? You might need to choose an extension that uses a background image and not just a color to hide that default coloration. Worth a try? I don't have Windows 7 so I can't test myself, but for example:

https://addons.mozilla.org/firefox/addon/topographic/

I realize that's a bit distracting, but does it cover up the default Aero colors?

Perfect thank you !

Thank you for reporting back. Hopefully you can find a design that suits your taste.