Examine source code of After Dark

{
  "manifest_version": 2,
  "version": "1.0",
  "name": "After Dark",
  "theme": {
    "images": {},
    "properties": {},
    "colors": {
      "toolbar": "rgb(14, 19, 27)",
      "toolbar_text": "rgb(255, 255, 255)",
      "frame": "rgb(17, 23, 34)",
      "tab_background_text": "rgb(94, 116, 123)",
      "toolbar_field": "rgb(19, 28, 42)",
      "toolbar_field_text": "rgb(94, 116, 123)",
      "tab_line": "rgb(70, 88, 128)",
      "popup": "rgb(19, 28, 42)",
      "popup_text": "rgb(255, 255, 255)",
      "tab_loading": "rgb(70, 88, 128)"
    }
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{ac874720-2abd-44b4-8f96-03c15ae1e5da}"
    }
  }
}