This script simulates the color style of the movie “300”:
https://en.wikipedia.org/wiki/300_%28film%29
The script is based on this how-to for PS with some improvements:
http://www.rickdavidson.com/2007/04/30/visual-effects-in-the-style-of-300/
Copy it into the scripts folder from GIMP, you will find it then under Filters → Artistic → Movie 300.
If you like it, hug someone.
An example can be found here.
Updates: