Even though I love geany, the lack of a true dark ui in windows was one of the main problems (if not the main one).

Finally I've found an easy trick to get a dark UI, so I'm sharing it here. It works with Geany 1.37 and probably with earlier versions using GTK2. No need for a GTK3 build.

Steps.

1. Go to the following page. It's a GTK2 dark theme for Inkscape. We're gonna basically use it for Geany. It works.

https://www.gnome-look.org/p/1304466/

2. Download the dark theme from the github repository. You have the link in the page linked in step 1. Or just click here:

https://github.com/SimBotBiz/inkscape-dark-theme

3. Go to '[Geany root folder]\share\themes\MS-Windows\gtk-2.0'. There you'll find a file called 'gtkrc'. Rename it as 'gtkrc-backup-original'.

4. In the zip file downloaded from github, go to share>themes>Ms-Windows>gtk-2-0. There you have both a file named 'gtkrc' and a folder named 'ui'. Copy both of them in the folder in the step 3.

5. And that's all. After it, Geany in windows should look like this:

https://postimg.cc/vg1kK22S