Examine source code of Custom Light

{
  "manifest_version": 2,
  "version": "1.0",
  "name": "Custom Light",
  "theme": {
    "images": {},
    "properties": {},
    "colors": {
      "toolbar": "rgb(235, 235, 235)",
      "toolbar_text": "rgb(50, 50, 50)",
      "frame": "rgb(75, 75, 75)",
      "tab_background_text": "rgb(255, 255, 255)",
      "toolbar_field": "rgb(255, 255, 255)",
      "toolbar_field_text": "rgb(50, 50, 50)",
      "tab_line": "rgb(235, 235, 235)",
      "popup": "rgb(235, 235, 235)",
      "popup_text": "rgb(50, 50, 50)",
      "tab_loading": "rgb(235, 235, 235)"
    }
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{ab675e68-7e1f-4eb6-b134-7ba372c972c1}"
    }
  }
}