A Dark theme for GTK
mkdir ~/.themes && mkdir ~/.icons
git clone https://github.com/SAGAtheme/GTK.git
cp -r GTK/themes/. ~/.themes
cp -r GTK/icons/. ~/icons
If you do not want pink as an accent colour you can edit the files themselves (open the folder(s) in an editor and replace all occurrences of #FFC2DF with your own accent) or use one of the older themes which offer multiple options for accent colour(s).