Examine source code of Default Tweaked

{
  "manifest_version": 2,
  "version": "1.0",
  "name": "default tweaked",
  "theme": {
    "images": {},
    "properties": {},
    "colors": {
      "toolbar": "rgb(43, 42, 51)",
      "toolbar_text": "rgb(251, 251, 254)",
      "frame": "rgb(28, 27, 34)",
      "tab_background_text": "rgb(251, 251, 254)",
      "toolbar_field": "rgb(28, 27, 34)",
      "toolbar_field_text": "rgb(255, 255, 255)",
      "tab_line": "rgba(111, 219, 38, 0)",
      "popup": "rgb(66, 65, 77)",
      "popup_text": "rgb(251, 251, 254)",
      "button_background_active": "rgb(91, 91, 102)",
      "button_background_hover": "rgb(82, 82, 94)",
      "icons_attention": "rgb(0, 221, 255)",
      "icons": "rgb(253, 253, 254)",
      "ntp_background": "rgb(43, 42, 51)",
      "ntp_text": "rgb(253, 253, 254)",
      "popup_border": "rgb(82, 82, 94)",
      "popup_highlight_text": "rgb(253, 253, 254)",
      "popup_highlight": "rgb(43, 42, 51)",
      "sidebar_border": "rgb(76, 76, 81)",
      "sidebar_highlight_text": "rgb(253, 253, 254)",
      "sidebar_highlight": "rgb(76, 76, 81)",
      "sidebar_text": "rgb(253, 253, 254)",
      "sidebar": "rgb(56, 56, 61)",
      "tab_background_separator": "rgba(0, 0, 0, 0)",
      "tab_loading": "rgb(0, 221, 255)",
      "tab_selected": "rgb(43, 42, 51)",
      "tab_text": "rgb(253, 253, 254)",
      "toolbar_bottom_separator": "rgb(12, 12, 13)",
      "toolbar_field_border_focus": "rgb(33, 143, 166)",
      "toolbar_field_border": "rgba(0, 0, 0, 0)",
      "toolbar_field_focus": "rgb(66, 65, 77)",
      "toolbar_field_highlight_text": "rgb(253, 253, 254)",
      "toolbar_field_highlight": "rgb(46, 113, 131)",
      "toolbar_field_separator": "rgba(0, 0, 0, 0)",
      "toolbar_field_text_focus": "rgb(253, 253, 254)",
      "toolbar_top_separator": "rgba(0, 0, 0, 0)",
      "toolbar_vertical_separator": "rgba(0, 0, 0, 0)"
    }
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{2b257a3c-e9b4-4354-a492-a9c2e8eda43f}"
    }
  }
}