Many times a complete theme is not needed but rather the ability to change a single or a couple of aspects of the UI color scheme yet it s so convoluted and nestled in the internal FF configuration that it takes googling to even get a clue how to. Let me give an example. In my case I do use a complete dark theme to go easy on my eyes and the addition of a default dark theme with FF57 is a very much appreciated one as it doesn't require me to muddy up my FF installation with a resource gobbling hodgepodge of third party add-ons or do edits in the bowels of the browser configuration files to make it work. However, the default dark theme STILL uses a white about:newtab page which tbh is a rather sloppy omission considering the effort of putting in a dark default theme at all. Granted it is semi-fixable but only by yet again mucking around in the bowels of the browser configuration. When the browser starts, the entire UI flashes white for a few seconds before custom color information is applied to it and pretty much the same occurs when you open a new tab or even sometimes when you simply switch between already opened tabs. Whats wrong with an old fashioned simple UI color options page with an old fashioned color picker in the settings to let the USER decide what color he or she wants on the various parts of the browser? Furthermore, it seems like the UI drawing bit of code needs apply custom color to the UI elements BEFORE they are actually displayed. That is all