Rated 4 out of 5 stars

I haven't seen this working yet.
It's not clear where you are getting the labels. I use gmail and carddav to keep my google contacts replicated in thunderbird. So the labels from gmail (and the color) are all in the address book.
I also saw someone ask if some labels like 'all' and 'unread' etc can be omitted to make the list short.
Looks like you got a good thing going.
Thanks.

This review is for a previous version of the add-on (0.2).