Examine source code of BillyXP

{
  "theme": {
    "images": {
      "theme_frame": "billyxphdr.jpg"
    },
    "colors": {
      "frame": "#808080",
      "tab_background_text": "#000000"
    }
  },
  "version": "2.0",
  "name": "BillyXP",
  "manifest_version": 2,
  "description": "Translucent firefox logo on a XP default color scheme matching background."
}