If the built-in screens are unreadable, you may need to modify an external settings file...

First, exit out of Firefox completely.

Type or paste the following in the Windows 7 Start menu search box and press Enter:

%APPDATA%\Mozilla\Firefox\Profiles

In that folder, you usually will find a single semi-randomly-named folder. If you find more than one, try to identify the most recently updated folder.

Inside that folder, you should find the prefs.js file (or if Windows is hiding the .js file extension, a file named prefs of type JScript). This contains many, many preferences, so ideally you would just remove the unwanted one.

To edit prefs.js, right-click it and choose Edit. Do not choose Open, as Windows will then try to execute the script.

Can you find this:

user_pref("browser.display.document_color_use", 1);

If Yes, change the 1 to a 2 and then save.

If No, you might be using a Windows "High Contrast" theme. Paste this whole line at the end of the file and save it:

user_pref("browser.display.document_color_use", 2);

At your next startup, Firefox should use only colors specified by web pages and not override them.

Can you open the about:preferences page nia the location/address bar and reach the content tab?

• about:preferences#content

Then you can open the colors window and change the colors.

Or open the about:config page and reset the browser.display.foreground_color via the right-click context menu to the default value

• about:config?filter=browser.display.foreground_color

Thanks for helpful and quickly answer. I just tried to press and guess and it was worked already. thankssssss