Recently Firefox decided to remove an add-on I have been using safely for years (Classic Theme Restorer). Not only does this mean I am stuck with icons where I would prefer text, it also seems to have removed the ability of the browser to respect my system settings properly. I need to work with a dark background and light text to prevent eyestrain and text. Previously I just ticked the "use system colours" box and everything was fine. Now if I have the this box ticked, many web pages are displayed with white background and black text. If I untick it and specify colours to use, the bulk of the web page displays correctly, but the scrollbar is light grey on a slightly darker grey, check boxes are white, buttons are white with black text, and this typein box has a hideous green background. I am using Firefox 56 on Linux Mint - I have deliberately not downgraded to a more recent version of Firefox, because they do not support Classic Theme restorer. Is there any way I can control the colours of widgets using about:config ?