Examine source code of Nature Walk

{
  "theme": {
    "images": {
      "theme_frame": "Nature-Walk-Heading.jpg"
    },
    "colors": {
      "frame": "rgba(229,230,232,1)",
      "tab_background_text": "#e3f20c"
    }
  },
  "version": "2.0",
  "name": "Nature Walk",
  "manifest_version": 2,
  "description": "Two people out for a walk on a winter's day at dusk."
}