Examine source code of 3 Day Respawn

{
  "theme": {
    "images": {
      "theme_frame": "header.png"
    },
    "colors": {
      "frame": "#000000",
      "tab_background_text": "#49b50e"
    }
  },
  "version": "2.0",
  "name": "3 Day Respawn",
  "manifest_version": 2,
  "description": "A Firefox theme for <a rel=\"nofollow\" href=\"https://outgoing.prod.mozaws.net/v1/61dff0b2088d12c1dbfef89691642fba32dadaa401fc8fc95320d92a9ec6186d/http%3A//3dayrespawn.com\">3dayrespawn.com</a>"
}