Examine source code of Small Blue Marble

{
  "theme": {
    "images": {
      "theme_frame": "Blue_Marble_header.png"
    },
    "colors": {
      "frame": "#d1d1d1",
      "tab_background_text": "#ffffff"
    }
  },
  "version": "2.0",
  "name": "Small Blue Marble",
  "manifest_version": 2,
  "description": "The Earth seen from the Apollo 17 mission -- the famous \"Blue Marble\" photograph."
}