I must second the review of 16 days ago. Once I get ten or more tabs open in Firefox 61, Colorful Tabs causes me to lose control of Firefox, as it continues to cycle through tabs all by itself. Impossible to stop this buggy add-on from taking control of Firefox. Once I disabled and removed Colorful Tabs, the random cycling through tabs ceased. This only happens once a lot of tabs are opened. But the bug is serious enough and disruptive enough that I made the decision to remove it.
I wasn't using it anyway. I liked the way it used to be where the tabs them selves were colored. I understand Mozilla changed their code, making the old implementation impossible to implement.