Tin, could you post the slow one?
I'd like to experiment it (obviously using very very small images....)

you asked for it...super slow (You need to have python installed and easygui library installed)

I only tested with pngs when i tried jpg i edited one pixel and near by pixel seemed to get affected so i stuck with pngs.. it'll output "out.png"

thanks Tin, downloaded: there is no "registration", how did you test it? interactively?

not sure what you mean by interactively.
I just have python installed on my computer with easygui library installed as well, and i run
python colortransfer.py
in command window
and then select image file and select color image file and let it run

If only i knew of a way to map colors that's more advanced than luminance...since luminance can combine colors of different hues in order next to each other....

I meant that it is not a registered gimp python plug-in.
I don't like command line.

maybe you can try using also "color proximity" by hue...

I tried converting it from RGB to HSV and ordered by value then by hue and by saturation and other orders too but nothing came out interesting.
Now i am trying something else...like starting with colors closest original to black in the LAB space and then finding closest source color to replace...
Interested in seeing what results look like but this process is magnitude slower... it might take like a day or longer to process your sample image.
I am just running it now...and it takes a little over a second to process one color and there are about 149,000 colors in the image.
All done using distance in LAB space.

good luck!....