Background and grid will not accept changes

Using windows 10 update (KB4541335) on Firefox 75.0 I have tried changing the background color and the grid color in the page toolbar in the page settings. The box, when clicked on, brings up choices. When selected the choices do not implement. I have tried restarting the program and the device. I am confused as to what to try next. Please advise of likely errors on my part. Please look at a fix on your part.

Are you using a language other than English? Some users have encountered this problem when their computer is set to another language. Set it to use English, change and save the setting, then set your computer back to your preferred language. If that is not the issue (or does not solve it), you can also try setting the preference in Chrome.