here's how to do it: paste this geany.css [geany.zip](https://github.com/geany/geany/files/11593367/geany.zip) into the \AppData\Roaming\geany folder. The css is the gtk-dark file from https://www.gnome-look.org/p/1013743/. there is no need to change the .css files on geany\data.
![image](https://github.com/geany/geany/assets/107224222/24fe116c-8e6b-4cf6-9e3d-6409...)