I always used the old colorful tabs scheme with a wide range of colors to choice, coloring any single tab in your own preferred color. So happy when I found this one for FF 57 - but unfortunately at the moment it does not work as before. So at the moment 3 of 5 stars to the developer and really zero stars for FF 57! So I think we all are patient and wait some time and one day Colorful Tabs will be back working as the old one - a very useful 5 stars tool.