Even as this thread is quite old, I think I can provide a simpler solution to change Geany to a dark theme if you don't mind change your theme to dark system-wide. Actually it has to done in two steps:
Even as this thread is quite old, I think I can provide a simpler solution to change Geany to a dark theme if you don't mind change your theme to dark system-wide. Actually it has to done in two steps: