I have now reinstalled geany from default ubuntu mint repositories, as maybe I had some screwed up installation. It is a pity that you don't provide linux binaries or ppa. The schemes now come up in the meny but say (null) and don't show any colours.
Debug Messages: 12:09:58: Geany INFO : Geany 1.32, en_US.UTF-8 12:09:58: Geany INFO : GTK 3.22.30, GLib 2.56.3 12:09:58: Geany INFO : System data dir: /usr/share/geany 12:09:58: Geany INFO : User config dir: /home/l/.config/geany 12:09:58: Geany INFO : System plugin path: /usr/lib/i386-linux-gnu/geany 12:09:58: Geany INFO : Added filetype Arduino (61). 12:09:58: Geany INFO : Added filetype Genie (62). 12:09:58: Geany INFO : Added filetype Clojure (63). 12:09:58: Geany INFO : Added filetype Scala (64). 12:09:58: Geany INFO : Added filetype CUDA (65). 12:09:58: Geany INFO : Added filetype Graphviz (66). 12:09:58: Geany INFO : Added filetype Cython (67). 12:09:58: Geany INFO : Added filetype JSON (68). 12:09:58: Geany INFO : Loaded libvte from libvte-2.91.so.0