Rated 4 out of 5 stars
I installed it and it worked straight away. One particular thing I would correct is when you single click on the email then the font in the line with subject, from, to etc is going white so it is hard to see which email is currently highlighted. Fortunately you can disable the stripped red-white background and font comes to black color so on the emails list the selected email is again highlighted in dark blue color. That is the reason I give it only 4 stars. Correct it and you will get 5 star from me :) Besides that - addon does what is supposed to do.
Reply to the author: I have seen higlighting emails with different colors (in yellow, red, whatever) in other addons, check XNote for instance. Fix shouldn't be that difficult .. I hope..
I know about that issue, but I can't fix it properly without the Thunderbird maintainers first making a fix to the core Thunderbird code.