Dark theme #16 (orange) seems to be miles better than all the rest, at least for my setup. The others just don't look too good for me on a startpage.com search. I run Linux Mint Cinnamon 18.3 with Mint-Y-Yltra Dark theme by the way, with Firefox sporting the regular Dark theme as well. Still, this is a great add-on. I kinda' feel bad for not rating 5 stars.