Great overall. Rated 5 out of 5 stars

Three things:

- The weird transparent close button makes this add-on visually incompatible with themes that use unique closers.

- The default setting for color should most definitely be most frequent color of icon.

- The opacities should be set to 20% for background and 60% for foreground to make it easier to differentiate between active and inactive tabs.

This review is for a previous version of the add-on (2.2).