Examine source code of Routemaster bell push

{
  "theme": {
    "images": {
      "theme_frame": "push_once_header4.jpg"
    },
    "colors": {
      "frame": "#a6947e",
      "tab_background_text": "#000000"
    }
  },
  "version": "2.0",
  "name": "Routemaster bell push",
  "manifest_version": 2,
  "description": "bell button on a London Routemaster bus"
}