Examine source code of Default

{
  "manifest_version": 2,
  "version": "1.0",
  "name": "Default Dark",
  "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(251, 251, 254)",
      "tab_line": "rgba(248, 112, 140, 0)",
      "popup": "rgb(66, 65, 77)",
      "popup_text": "rgb(251, 251, 254)",
      "popup_border": "rgb(82, 82, 94)",
      "popup_highlight": "rgb(43, 42, 51)",
      "tab_selected": "rgb(66, 65, 77)",
      "toolbar_field_focus": "rgb(66, 65, 77)",
      "tab_loading": "rgba(248, 112, 140, 0)"
    }
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{d282455d-f7e3-4d4e-a0c2-c3994fda61dc}"
    }
  }
}