Examine source code of Danube river

{
  "theme": {
    "images": {
      "theme_frame": "Duna6.jpg"
    },
    "colors": {
      "frame": "#0e2b12",
      "tab_background_text": "#f1f5ed"
    }
  },
  "version": "2.0",
  "name": "Danube river",
  "manifest_version": 2
}