A map in KGeography is made by two files, one is the image of the map and the other one is its description.
You can find here a tool (made by Yann Verley) which helped him with the map of France. To find out its usage, simply execute it and read the help message. It basically creates the
.kgm file from a plain text file and creates a file with the colors it has assigned to each division, so you can fill the map according to them.
There is another tool colorchecker.py written by Albert Astals Cid. You need PyQt4 to run this. Just run this with the .kgm filename as argument (you also need the .png file of the map in the same folder). This will tell you if any pixel on the map has a different color which is not defined in the .kgm (description) file.
Please read also the tutorial How to add maps on the KGeography website.