Examine source code of Old-World

{
  "manifest_version": 2,
  "version": "1.0",
  "name": "Old-World",
  "theme": {
    "images": {},
    "properties": {},
    "colors": {
      "toolbar": "rgb(40, 46, 51)",
      "toolbar_text": "rgb(37, 219, 202)",
      "frame": "rgb(24, 25, 29)",
      "tab_background_text": "rgb(255, 255, 255)",
      "toolbar_field": "rgb(24, 25, 29)",
      "toolbar_field_text": "rgb(37, 219, 202)",
      "tab_line": "rgba(255, 255, 255, 0)",
      "popup": "rgb(40, 46, 51)",
      "popup_text": "rgb(37, 219, 202)",
      "tab_loading": "rgba(255, 255, 255, 0)"
    }
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{cab85ffe-96db-40b2-9cd3-0ce65d253c3c}"
    }
  }
}