Inside the folder that has the name of the livery, there's a sub-folder called 'objects,' and THAT's where the actual image files for the repaint are contained. For instance, if a folder inside the 'liveries' folder is called 'Metallic Blue', then this is one option you will see in the livery selector in X-plane. This folder name is what's used in X-Plane in the selection dialog. The first sub-folder that contains the livery will bear the name of that livery. For this, please check out the 'liveries' folder, and take a look at the existing liveries. Second, it is important to familiarize yourself with the file and folder structure of repaints. Photoshop or Gimp is an essential tool for repaints.