Examine source code of rain and lightning

{
  "theme": {
    "images": {
      "theme_frame": "raintop.jpg"
    },
    "colors": {
      "frame": "#6e6d6d",
      "tab_background_text": "#f5f5f5"
    }
  },
  "version": "2.0",
  "name": "rain and lightning",
  "manifest_version": 2,
  "description": "rainy day in your firefox"
}