Examine source code of Congruent Grey

{
  "theme": {
    "images": {
      "theme_frame": "header.png"
    },
    "colors": {
      "frame": "#606060",
      "tab_background_text": "#202020"
    }
  },
  "version": "2.0",
  "name": "Congruent Grey",
  "manifest_version": 2,
  "description": "Inspired by Atle Mo's background from <a rel=\"nofollow\" href=\"https://outgoing.prod.mozaws.net/v1/b6f8658694f689b153eafda8edc3d65966b5bbb91410041f9a56153cc076279e/http%3A//subtlepatterns.com/congruent-pentagon\">subtlepatterns.com/congruent-pentagon</a>"
}