Photoshop
Basically, you are just recoloring them. You clone the item you want to recolor. The file will be in the documents/sims 2/projects folder. Open that with your editing program (like Paint Shop Pro,
Photoshop, etc.). Recolor at will. Once done, save, and then, in Body Shop, refresh the image (little circling arrow underneath). The item should now show the changes. If not happy, go edit some more, refreshing as needed. Once done, add to game, filling in whatever you need to.
