This was a 5 star extension before FF57, now we have a significantly faster browser but with a shockingly bad user interface particularly the poor tab placement (fixed with a chrome css bodge) and Colorful Tabs functionality is not even remotely like it was before. I have currently disabled this extension, switched to FF dark theme and with a wider tab text space.

Would have possibly reverted to FF56 but even witha 'new' install it's impossible to install and then disable upgrades before the FF57 upgrade is downloaded.