EDIT 28-04-2016: I've added an amber-colored version of the 'Retro'-theme to this post. You can find the download at the bottom, next to the other .zip-archives
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As most people probably know, you can change the way the AppGameKit looks by selecting 'View > Change Color Scheme'. Doing so changes the way your code is presented. Selecting a Scheme however, doesn't change the way IDE itself looks (buttons, tabs, panels etc.).
Recently, I was looking for some dark themes. I found several on the Geany forums and decided to make matching IDE-files. Attached to this post are the colorschemes I liked and their IDE's.
(Tango Dark)

(InkPot)

(Steampunk)

(Retro)

(Retro-Amber)
Installing the schemes is simple: unzip the contents of one of the scheme's in AGK's installation folder*. Merge and Overwrite files if you are prompted to do so. After this, the IDE should have a new look. Next, select the corresponding colorscheme using 'View > Change Color Scheme'.
Uninstallation is simple as well: locate the file 'geany.gtkrc' in the folder 'App Game Kit 2 > Tier 1 > Editor > Data', and delete it.
Enjoy!
*: Default installation folders are: "C:\Program Files (x86)\Steam\SteamApps\common\App Game Kit 2\" (
Steam) or "C:\Program Files (x86)\The Game Creators\AGKV2\" (
Stand-alone version)