I loved this "pre-57+". Now, installing it somehow messes with themes, and blanks the menu, the colors bleed into all tabs, instead of being on single tabs, and as of the "latest" Firefox version, this was the one, and only one, addon I disabled to stop the browser going spastic at random. What do I mean by spastic? Well, basically, when clicking on a tab, with several open, Firefox randomly "lost track" of which tab is was on, and kept flipping through them, either between two different tabs, the one that was open before, or the new one, or, if I tried to then click more, through each one of them, rapidly, cycling over and over, with no way to stop them, short of closing all but one tab, or killing the browser.
Its like, it tried to update the color on all tabs, but something in the way the new version of FF works causes it to "only" update each one if "currently visible", so trying to do so causes them to cycle through every tab you try to click on. Very, very odd.. Can't recommend this one any more, even if this issue is fixed, because it hasn't behaved as originally intended for many FF versions now. And maybe, due to changes in the browser itself, can't, like so many others that where once wonderful addons, or practically a necessity (Tab Mix, for example).