In that demo, I use KML files (one per country), and enable management of it.
If you just want to show countries by some color, you can do:
1 - create or find KML files for your countries with filled by your color
2 - upload to server in folder, where you can access from web
3 - create paths (one per file), in KML tab enter full path to your file (with http:), not relative
4 - and don't forget about Google Maps API restrictions for KML files (size etc)
As for me - I found free files (for non commercial use). I think you can find it too, and, you can edit it for example in Google Earth
Don't forget support my developments: post review in JED, donate