Examine source code of Dark Petrol

{
  "name": "Dark Petrol",
  "manifest_version": 2,
  "version": "1.0",
  "theme": {
    "images": {
      "theme_frame": "FF_Header_Dark_Petrol.png"
    },
    "colors": {
      "frame": "rgba(18, 38, 48, 1)",
      "tab_background_text": "rgba(63, 112, 117, 1)",
      "toolbar": "rgba(13, 21, 23, 1)",
      "bookmark_text": "rgba(134, 194, 204, 1)",
      "toolbar_field": "rgba(18, 38, 48, 1)",
      "toolbar_field_text": "rgba(134, 194, 204, 1)",
      "tab_line": "rgba(10, 24, 26, 1)"
    }
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{b8a56fa9-3a60-4ce7-8cb3-47fdb5b72000}"
    }
  }
}