Examine source code of Calm and Carry

{
  "theme": {
    "images": {
      "theme_frame": "KeepCalm.png"
    },
    "colors": {
      "frame": "#ff0000",
      "tab_background_text": "#000000"
    }
  },
  "version": "2.0",
  "name": "Calm and Carry",
  "manifest_version": 2,
  "description": "British World War II poster that has enjoyed a huge renaissance"
}