I find this very unfriendly to those of us with suboptimal vision.

Instead of just giving each tab a different color, which is the way the developer describes it, this extension turns everything from the top of the window to the top of the web page the same color, and leaves all of the rest of the tabs white with black lettering. In other words, clicking on the first tab makes that tab and the rest of the top of the window Color 1, activating the second tab makes the second tab and the rest of the top of the window Color 2, etc.

The developer makes it sound like the tabs all have different colors even when inactive, which would have helped me distinguish between tabs without having to read the teeny tiny print on each one. It does ease my difficulty reading tiny white lettering on a black background, so at least Colorful Tabs does help, but black letters on most of the tab colors are almost as hard to read as white letters on a black background.

I'm just sorry I didn't notice that my settings had changed to automatic updates, because now I'll have to wait six months for enough extensions to be developed to make Firefox usable for me. In the meantime, I guess I'll go back to Safari for a while with my tail tucked between my legs.