Examine source code of Twitter Classic

{
  "theme": {
    "images": {
      "theme_frame": "twitter-persona-by-aalaap-header.png"
    },
    "colors": {
      "frame": "rgba(229,230,232,1)",
      "tab_background_text": "#000"
    }
  },
  "version": "2.0",
  "name": "Twitter Classic",
  "manifest_version": 2,
  "description": "A Twitter persona that will give you a seamless experience when using <a rel=\"nofollow\" href=\"https://outgoing.prod.mozaws.net/v1/26ca20fd517be4e3078c65b14f44521b572c8c48532db6c37d90ff3a2ee15167/http%3A//Twitter.com\">Twitter.com</a>!\n\nNote: This was intended to be used with the classic Twitter design around 2006-2009. It doesn't look quite the same now, but I'll keep it up for posterity!"
}