Examine source code of Cloud night sky

{
  "manifest_version": 2,
  "version": "1.0",
  "name": "Cloudy night sky",
  "theme": {
    "images": {
      "additional_backgrounds": [
        "images/0.png"
      ]
    },
    "properties": {
      "additional_backgrounds_alignment": [
        "right top"
      ],
      "additional_backgrounds_tiling": [
        "repeat"
      ]
    },
    "colors": {
      "toolbar": "rgb(9, 9, 9)",
      "toolbar_text": "rgba(0, 249, 245, 0.92)",
      "frame": "rgb(28, 30, 30)",
      "tab_background_text": "rgb(255, 255, 255)",
      "toolbar_field": "rgb(255, 255, 255)",
      "toolbar_field_text": "rgb(31, 32, 43)",
      "tab_line": "rgb(255, 231, 0)",
      "popup": "rgb(255, 255, 255)",
      "popup_text": "rgb(27, 26, 162)",
      "tab_loading": "rgb(255, 231, 0)"
    }
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{8b445c88-c399-46a4-a849-bbe5d4135776}"
    }
  }
}