Examine source code of Birds & Nature background

{
  "manifest_version": 2,
  "version": "1.0",
  "name": "Birds",
  "theme": {
    "images": {
      "additional_backgrounds": [
        "images/0.png"
      ]
    },
    "properties": {
      "additional_backgrounds_alignment": [
        "center center"
      ],
      "additional_backgrounds_tiling": [
        "repeat"
      ]
    },
    "colors": {
      "toolbar": "rgb(45, 154, 112)",
      "toolbar_text": "rgb(255, 0, 153)",
      "frame": "rgb(45, 154, 112)",
      "tab_background_text": "rgb(255, 255, 255)",
      "toolbar_field": "rgb(45, 138, 154)",
      "toolbar_field_text": "rgb(255, 255, 255)",
      "tab_line": "rgb(255, 0, 153)",
      "popup": "rgb(45, 154, 112)",
      "popup_text": "rgb(31, 0, 255)",
      "button_background_active": "rgb(81, 25, 58)",
      "button_background_hover": "rgb(32, 87, 97)",
      "icons": "rgb(45, 138, 154)",
      "ntp_background": "rgb(36, 106, 79)",
      "ntp_text": "rgb(32, 87, 97)",
      "tab_loading": "rgb(255, 0, 153)"
    }
  }
}