Rated 4 out of 5 stars

This addon is really nifty, I like it a lot.
However, there is a bug that is just a little to annoying to just live with it:
After a while having it active, the font-color in all menus changes to a gray that makes it really hard to read on the black background.
I tried
font-color: #66780D;
and
color: #66780D;
in the CSS-Style config for each menu, but it isn´t accepted. Shouldn´t be necessary anyway to do that.

Additional information for the developer:
I dont use the CSS feature otherwise.
System: Ubuntu 16.04 64-bit
Firefox: no modifications other than several addons.
Potentially conflicting installed addon: Tabmix Plus (has menu editing, too).

Otherwise, great addon!

This review is for a previous version of the add-on (5.03). 

Please send your bug-report to forums mozillaZine:
http://forums.mozillazine.org/viewtopic.php?t=2828771