Examine source code of Leather Light-Grey FF

{
  "theme": {
    "images": {
      "theme_frame": "header.jpg"
    },
    "colors": {
      "frame": "#aaaaaa",
      "tab_background_text": "#000000"
    }
  },
  "version": "2.0",
  "name": "Leather Light-Grey FF",
  "manifest_version": 2,
  "description": "Leather texture in light grey with Firefox logo"
}