User blog comment:MrHobit1234/Prepare the Lawyers/@comment-27219153-20170211232328/@comment-25841881-20170214020650

Gimp would work great for doing it the way camp describes, as you could select all the pixels of that exact shade and do a recolour. And potentially shift every pixel on the image, though I don't remember if it was Gimp I've done that it.