Examine source code of Dark Hearthstone

{
  "name": "Dark Hearthstone",
  "manifest_version": 2,
  "version": "4.0",
  "theme": {
    "images": {
      "theme_frame": "YMvSr.jpg"
    },
    "colors": {
      "toolbar": "rgba(148, 112, 44, 0.27)",
      "toolbar_field": "rgba(173, 31, 121, 0)",
      "toolbar_field_text": "rgba(158, 128, 30, 1)",
      "frame": "rgba(255, 196, 0, 1)",
      "tab_background_text": "rgba(219, 64, 64, 1)",
      "bookmark_text": "rgba(0, 89, 255, 1)"
    }
  }
}