"do not use Classic Theme Restorer. It has a tab color function that colors tab selected, read, unread, etc, but will not color all the tabs at random or by domain. It conflicts with colorful tabs and the function cannot be turned off."
Uhh. I'm using it with CT and it's just fine! No conflict whatsoever. And with that add on, you can choose whether you want the ugly square tabs or the rounded ones. Although, it only rounds the active one.