With this new version of Firefox 57.0, the browser is lacking any kind of style.
The program icons are basically stick figures.
The tabs are plain white square boxes.
The screen background is a plain white or grey or black. At least you can customize the menu bar.
Where has all the customizable style gone?
I used to be able to use Noia icons which were a litle whimsical but fun.
I used to be able to use Colorful Tabs to customize the look of the tabs and give the screen some useful color.
Those addons have been slowly disabled with each new version.
Luckily websites have customized icons but the folder icons in the bookmarks again are plain stick figures.
Sure, the browser should not always be in the foreground so as to not detract from the page you are viewing.
None the less, the style of Firefox has turned into a blank piece of paper where you aren't able to change the look and feel.