Does anyone know how to create faction colours for unit icons using Gimp

[onmy6]

I've modded some units to turn into mercenary units and then allocated them to various factions and I'm trying to alter the unit icons to change to faction colours, I'm using "Gimp" but am having no luck.

I've tried changing the unit icons jacket to transparent, then tried setting the jacket to black and then tried setting it to white in the vain hope it might do something. I've copied the alpha channel to the unit icon mask and deleted the unit icon jacket alpha channel colour on the icon itself and various other things in trial and error but nothing

Does anyone know how to do this using Gimp?

[onmy6]

Never mind I figured it out in the end with abit more trial and error.
Many thanks to those who had a look at the post