Examine source code of Merlin Header

{
  "theme": {
    "images": {
      "theme_frame": "firefoxbgwoot.JPG"
    },
    "colors": {
      "frame": "#000000",
      "tab_background_text": "#bf0000"
    }
  },
  "version": "2.0",
  "name": "Merlin Header",
  "manifest_version": 2,
  "description": "Merlin is a BBC show that I watch and I love this picture so I tried as hard as I could to make look good as a header :)"
}