This script simulates the 2 Color Technicolor effect.
Copy it into the scripts folder from GIMP, you will find it then under Colors → Technicolor 2 Color. Examples here and here:
Updates:
gimp -i -b '(elsamuko-technicolor-2-color-batch "picture.jpg" 0.97 FALSE 1 0.5 0 255 255 255 0 0 255 255 0 TRUE)' -b '(gimp-quit 0)'
gimp -i -b '(elsamuko-technicolor-2-color-batch "*.jpg" 0.97 FALSE 1 0.5 0 255 255 255 0 0 255 255 0 TRUE)' -b '(gimp-quit 0)'
See also the Technicolor 3 Color Script.