Examine source code of Nighttime

{
  "manifest_version": 2,
  "version": "1.0",
  "name": "Nighttime",
  "theme": {
    "images": {
      "additional_backgrounds": [
        "images/0.jpg",
        "images/1.jpg"
      ]
    },
    "properties": {
      "additional_backgrounds_alignment": [
        "center center",
        "center center"
      ],
      "additional_backgrounds_tiling": [
        "repeat",
        "repeat"
      ]
    },
    "colors": {
      "toolbar": "rgba(31, 23, 72, 0.34)",
      "toolbar_text": "rgb(189, 215, 243)",
      "frame": "rgb(36, 16, 163)",
      "tab_background_text": "rgb(189, 215, 243)",
      "toolbar_field": "rgba(27, 30, 60, 0.5)",
      "toolbar_field_text": "rgb(195, 217, 241)",
      "tab_line": "rgb(0, 0, 0)",
      "popup": "rgb(31, 34, 61)",
      "popup_text": "rgb(215, 226, 239)",
      "ntp_background": "rgb(4, 6, 69)",
      "ntp_text": "rgb(255, 255, 255)",
      "tab_loading": "rgb(0, 0, 0)"
    }
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{4c29a2d2-e10b-4c16-9cb1-781ebef8abd6}"
    }
  }
}