Works on Fennec Firefox for Android right away and there's so many customisable options. You can change the colour of the text or the background to any conceivable shade. You set a timer for activation and deactivation, disable or enable it for some sites, adjust contrast, brightness, enable and adjust sepia tone or grayscale and lots more. Personally I have not encountered any of these problems but some people have talked about how it doesn't work all the time everywhere that might be true and if it doesn't work for any text input box and if the colour of the text matches the background then I suppose text colour could be changed to some other colour other than white or black. For me it has worked perfectly thus far and I have not encountered any of the aforementioned problems.