Exactly what the previous reviews have said about this add-on with FF57 ("Quantum"), especially jazzybob:

ColorfulTabs does not work the same way as it did in the earlier versions of Firefox. In version 57 it highlights the tab your on with one color wile the rest of the tabs stay white.In addition the Bookmarks Toolbar and Addons Toolbars change the same color as the the highlighted tab. It's not pretty.

The one thing I loved about the old ColorfulTabs is the I could color code similar site tabs with the same color. Color coding allowed me to find tabs easily, as I can have 30 - 40 tabs open. Thank goodness for Firefox 57.

I'm very disappointed in this version of Colorful tabs and hope that they go back to the old way it worked. I'm uninstalling this version.

---> I won't use this extension any longer until it is fixed to the way it was before / how it is supposed to work!