Spartan-III Rubila

Its been since I first arrived here on DA that I haven't done much sprite work, and when I found out about Halo: Out With a Whimper ( [link] ) something in my head wanted me to recolour and slightly edit a sprite sheet again and the end result is what you see above.
The sprite sheet was found here ( [link] ) and I've found it quite a fun thing to do. Don't expect me to do any sheets for any of you though because I'm a lazy sod even if you paid me.
This of course isn't the final result, but I'll upload an updated version of it when I've done enough work on the modified sheet. Everything but the front view of the Hardened UpLink (HUL [3]) attachment was on the original sheet that belongs to its owner.
Rubila is what I usually call my female spartan and the name orginated from an RP I had from where an AI had the body shape of one of his OCs while the personality of one of my OCs while they were a captive of hunters. We put both names together and Rubila has stuck with me as a proper name ever since.
All the way here at the bottom, huh? Well while you're here, you may as well watch this [link] which is quite a WTF moment in Mass Effect 2 and is quite a mood lifter in the dark story it holds. Then again Garrus in ME 2 is usually quiet the fun Turian to talk to and listen to what he has to say
EDIT 1: Made the background transparent so that it'd be easier for someone to try and edit themselves. And on to my first question. Can you use GIMP to replace all of a certain colour with another one? If so please tell me how to do it.