Examine source code of Dark Crossing

{
  "name": "Animal Crossing Dark",
  "manifest_version": 2,
  "version": "7.0",
  "theme": {
    "images": {
      "theme_frame": "AC Firefox.png"
    },
    "colors": {
      "frame": "rgba(20, 20, 20, 1)",
      "tab_background_text": "rgba(255, 255, 255, 1)",
      "toolbar": "rgba(49, 49, 51, 0.7)",
      "bookmark_text": "rgba(255, 255, 255, 1)",
      "toolbar_field": "rgba(79, 79, 82, 1)",
      "toolbar_field_text": "rgba(255, 255, 255, 1)"
    }
  }
}