Code:
# uname -a
Linux myserver 4.9.0-13-amd64 #1 SMP Debian 4.9.228-1 (2020-07-05) x86_64 GNU/Linux
MATE 1.16.2 BlackMATE theme with Dopple Window Border.
I prefer a dark theme. It's easier on my eyes.
Everything else in Bluefish will change, but not the background.
Edit > Preferences > Fonts & Colors > Background color
I change this to a dark color, and nothing happens. Again, I can change the font color, or cursor color, or font size, or anything else, but not the background color.
I have also gone into "Text styles" it also does nothing.