Examine source code of Happy Halloween

{
  "name": "Happy Halloween",
  "manifest_version": 2,
  "version": "1.0",
  "theme": {
    "images": {
      "theme_frame": "Before.png"
    },
    "colors": {
      "frame": "rgba(84, 113, 179, 1)",
      "tab_background_text": "rgba(0, 0, 0, 1)",
      "toolbar": "rgba(31, 222, 127, 1)",
      "bookmark_text": "rgba(255, 8, 8, 1)",
      "toolbar_field": "rgba(230, 184, 18, 1)",
      "toolbar_field_text": "rgba(255, 0, 0, 1)",
      "tab_line": "rgba(255, 0, 0, 1)"
    }
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{a7fad487-7f10-4347-a22d-66a045a634be}"
    }
  }
}