Examine source code of Gorrors

{
  "theme": {
    "images": {
      "theme_frame": "persona.png"
    },
    "colors": {
      "frame": "#8c8c8c",
      "tab_background_text": "#1378ab"
    }
  },
  "version": "2.0",
  "name": "Gorrors",
  "manifest_version": 2,
  "description": "Add some evil to your Firefox with this scary persona!"
}