Examine source code of Google Sketch

{
  "theme": {
    "images": {
      "theme_frame": "Google-Sketchboard.jpg"
    },
    "colors": {
      "frame": "#000000",
      "tab_background_text": "#000000"
    }
  },
  "version": "2.0",
  "name": "Google Sketch",
  "manifest_version": 2,
  "description": "Found an image of a massive blackboard where many Google brainstorming occurred. Since it wasn't at all copyrighted or owned, I decided to use it as a persona theme. Enjoy."
}