Examine source code of Towel Colours

{
  "manifest_version": 2,
  "version": "1.1",
  "name": "Towel Colours",
  "theme": {
    "images": {
      "additional_backgrounds": [
        "images/bg-000-5672c42860d5b06e1058dc477397f3ef.svg"
      ]
    },
    "properties": {
      "additional_backgrounds_alignment": [
        "top"
      ],
      "additional_backgrounds_tiling": [
        "repeat"
      ]
    },
    "colors": {
      "toolbar": "rgb(99, 130, 151)",
      "toolbar_text": "rgb(255, 255, 255)",
      "frame": "rgb(53, 53, 77)",
      "tab_background_text": "rgb(223, 147, 8)",
      "toolbar_field": "rgb(99, 130, 151)",
      "toolbar_field_text": "rgb(27, 27, 41)",
      "tab_line": "rgba(248, 165, 0, 0)",
      "popup": "rgb(53, 53, 77)",
      "popup_text": "rgb(255, 255, 255)",
      "button_background_active": "rgb(223, 147, 8)",
      "icons_attention": "rgb(53, 53, 77)",
      "ntp_background": "rgb(53, 53, 77)",
      "popup_border": "rgb(27, 27, 41)",
      "popup_highlight": "rgb(99, 130, 151)",
      "scrollbar-color": "cadetblue steelblue",
      "sidebar_border": "rgb(27, 27, 41)",
      "sidebar_highlight": "rgb(99, 130, 151)",
      "sidebar": "rgb(56, 94, 119)",
      "toolbar_bottom_separator": "rgb(27, 27, 41)",
      "toolbar_field_border_focus": "rgb(53, 53, 77)",
      "toolbar_field_border": "rgb(53, 53, 77)",
      "toolbar_field_focus": "rgb(223, 147, 8)",
      "toolbar_field_highlight": "rgb(99, 130, 151)",
      "tab_loading": "rgba(248, 165, 0, 0)"
    }
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{651fb228-c1dc-4347-a6d7-1f91849a9528}"
    }
  }
}