Examine source code of Sunset - Setting sun

{
  "manifest_version": 2,
  "version": "1.0",
  "name": "Setting sun",
  "theme": {
    "images": {
      "additional_backgrounds": [
        "images/0.jpg"
      ]
    },
    "properties": {
      "additional_backgrounds_alignment": [
        "center center"
      ],
      "additional_backgrounds_tiling": [
        "no-repeat"
      ]
    },
    "colors": {
      "toolbar": "rgba(255, 252, 235, 0.5)",
      "toolbar_text": "rgb(109, 47, 0)",
      "frame": "rgb(255, 205, 132)",
      "tab_background_text": "rgb(0, 0, 0)",
      "toolbar_field": "rgba(255, 255, 255, 0.5)",
      "toolbar_field_text": "rgb(172, 43, 0)",
      "tab_line": "rgb(150, 80, 26)",
      "popup": "rgb(255, 255, 238)",
      "popup_text": "rgb(200, 82, 0)",
      "tab_loading": "rgb(150, 80, 26)"
    }
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{aa4ea4e2-7487-4e38-9d73-6fe18df3849c}"
    }
  }
}