Examine source code of Horizon for Firefox

{
  "name": "Horizon for Firefox",
  "manifest_version": 2,
  "version": "1.0",
  "theme": {
    "images": {
      "theme_frame": "58443865_1269581809864383_8964961872042262528_n.jpg"
    },
    "colors": {
      "frame": "rgba(28, 30, 38, 1)",
      "tab_background_text": "rgba(233, 83, 120, 1)",
      "toolbar": "rgba(28, 30, 38, 1)",
      "bookmark_text": "rgba(235, 218, 218, 1)",
      "toolbar_field": "rgba(35, 37, 48, 1)",
      "toolbar_field_text": "rgba(235, 218, 218, 1)"
    }
  }
}