Examine source code of Simple Night

{
  "manifest_version": 2,
  "version": "1.0",
  "name": "Simple Night",
  "theme": {
    "images": {
      "additional_backgrounds": [
        "images/bg-000-5672c42860d5b06e1058dc477397f3ef.svg"
      ]
    },
    "properties": {
      "additional_backgrounds_alignment": [
        "top"
      ],
      "additional_backgrounds_tiling": [
        "repeat"
      ]
    },
    "colors": {
      "toolbar": "rgb(21, 26, 26)",
      "toolbar_text": "rgb(188, 194, 209)",
      "frame": "rgb(12, 12, 13)",
      "tab_background_text": "rgb(255, 255, 255)",
      "toolbar_field": "rgb(0, 0, 0)",
      "toolbar_field_text": "rgb(188, 194, 209)",
      "tab_line": "rgb(21, 26, 26)",
      "popup": "rgb(17, 18, 18)",
      "popup_text": "rgb(188, 194, 209)",
      "button_background_active": "rgb(21, 26, 26)",
      "button_background_hover": "rgb(34, 34, 34)",
      "ntp_background": "rgb(21, 16, 16)",
      "ntp_text": "rgb(255, 255, 255)",
      "popup_highlight_text": "rgb(188, 194, 209)",
      "popup_highlight": "rgb(37, 39, 39)",
      "sidebar_border": "rgb(48, 48, 48)",
      "sidebar_highlight_text": "rgb(22, 22, 22)",
      "sidebar_highlight": "rgb(48, 48, 48)",
      "sidebar": "rgb(16, 16, 16)",
      "toolbar_field_border_focus": "rgb(22, 22, 22)",
      "toolbar_field_focus": "rgb(22, 22, 22)",
      "toolbar_field_highlight": "rgb(37, 39, 39)",
      "toolbar_field_separator": "rgb(22, 22, 22)",
      "toolbar_vertical_separator": "rgb(21, 26, 26)",
      "tab_loading": "rgb(21, 26, 26)"
    }
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{96289970-9adb-4707-9dcb-475dde09c552}"
    }
  }
}