Rated 5 out of 5 stars

This is the best Thunderbird theme! Nonetheless, can it be modified? Specifically, can the light grey color on the Mail Toolbar and the light grey color when composing a new message be changed to a darker color?

*UPDATE 11/13/2018*
This theme is a awesome! Conema's assistance on how to change the light grey color on the Mail Tooblbar has been great.

This review is for a previous version of the add-on (1.1.5). 

Yes, it can be changed by editing the userChrome.css[1] file. I received some complaints about that gray color, if you have some spare time, you could open an issue in GitHub for discuss a color change.

[1]https://support.mozilla.org/it/questions/1160703