Examine source code of Twilight

{
  "manifest_version": 2,
  "version": "1.0",
  "name": "Twilight",
  "theme": {
    "images": {
      "additional_backgrounds": [
        "images/0.jpg"
      ]
    },
    "properties": {
      "additional_backgrounds_alignment": [
        "center top"
      ],
      "additional_backgrounds_tiling": [
        "repeat"
      ]
    },
    "colors": {
      "toolbar": "rgba(39, 58, 60, 0.39)",
      "toolbar_text": "rgb(151, 170, 148)",
      "frame": "rgb(22, 54, 75)",
      "tab_background_text": "rgb(113, 156, 158)",
      "toolbar_field": "rgba(0, 0, 0, 0.2)",
      "toolbar_field_text": "rgb(216, 209, 189)",
      "tab_line": "rgb(28, 171, 176)",
      "popup": "rgba(31, 31, 31, 0.97)",
      "popup_text": "rgb(113, 156, 158)",
      "tab_loading": "rgb(28, 171, 176)"
    }
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{a33b6d1c-b546-4527-925b-e8ecb6fce77f}"
    }
  }
}