Examine source code of Setting Sunset

{
  "manifest_version": 2,
  "version": "1.0",
  "name": "Setting Sun",
  "theme": {
    "images": {
      "additional_backgrounds": [
        "images/0.jpg"
      ]
    },
    "properties": {
      "additional_backgrounds_alignment": [
        "left center"
      ],
      "additional_backgrounds_tiling": [
        "repeat"
      ]
    },
    "colors": {
      "toolbar": "rgba(30, 74, 219, 0.06)",
      "toolbar_text": "rgb(1, 56, 255)",
      "frame": "rgb(142, 179, 201)",
      "tab_background_text": "rgb(0, 0, 0)",
      "toolbar_field": "rgba(255, 255, 255, 0.24)",
      "toolbar_field_text": "rgb(0, 0, 0)",
      "tab_line": "rgb(248, 207, 10)",
      "popup": "rgb(249, 159, 1)",
      "popup_text": "rgb(2, 2, 3)",
      "tab_loading": "rgb(248, 207, 10)"
    }
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{c03c3e9d-da2a-4012-b8ee-2704aa96aa89}"
    }
  }
}