Examine source code of happy rainy day

{
  "theme": {
    "images": {
      "theme_frame": "rain.jpg"
    },
    "colors": {
      "frame": "#ffffff",
      "tab_background_text": "#043482"
    }
  },
  "version": "2.0",
  "name": "happy rainy day",
  "manifest_version": 2,
  "description": "画用紙を切り貼りしたものを基に作成しました。"
}