Examine source code of Rainbow tree

{
  "theme": {
    "images": {
      "theme_frame": "rainbowtree.jpg"
    },
    "colors": {
      "frame": "#ffd500",
      "tab_background_text": "#ffffff"
    }
  },
  "version": "2.0",
  "name": "Rainbow tree",
  "manifest_version": 2,
  "description": "色違いもあります。"
}