That's unusual!

Does your system have any time-of-day theme transitions that could switch to dark backgrounds in the evenings?

Do any of your extensions modify website colors?

Have you created a userContent.css file to modify web page styles?

no I don't have any of those

Could you test in Firefox's Safe Mode? In its Safe Mode, Firefox temporarily deactivates extensions, hardware acceleration, any userChrome.css/userContent.css files, and some other advanced features to help you assess whether these are causing the problem.

If Firefox is running: You can restart Firefox in Safe Mode using either:

• "3-bar" menu button > "?" Help button > Restart with Add-ons Disabled
• (menu bar) Help menu > Restart with Add-ons Disabled

and OK the restart.

If Firefox is not running: Hold down the Shift key when starting Firefox. (On Mac, hold down the option/alt key instead of the Shift key.)

Both scenarios: A small dialog should appear. Click "Start in Safe Mode" (not Refresh).

Any improvement?

no I've still got the same issue

You can check the default colors in Options/Preferences.

• Options/Preferences -> General: Fonts & Colors -> Colors

Make sure you haven't enabled a High Contrast theme in the OS Accessibility settings.

Make sure you allow pages to choose their own colors.

• Options/Preferences -> General: Fonts & Colors -> Colors: "Override the colors specified by the page with my selections above"

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

no im still having the same issue

Hello!

Have you tried re-installing Firefox?

Boot the computer in Windows Safe Mode with network support to see if that has effect.

• https://www.bleepingcomputer.com/tutorials/how-to-start-windows-in-safe-mode/
• https://www.7tutorials.com/4-ways-boot-safe-mode-windows-10