如何在Flutter中更改单选控件的边框颜色？

ThemeData customTheme = ThemeData(
  // 设置主题的颜色
  primaryColor: Colors.blue,
  accentColor: Colors.blue,
  // 设置单选控件的边框颜色
  radioTheme: RadioThemeData(
    fillColor: MaterialStateColor.resolveWith((states) => Colors.blue),
  ),
);

void main() {
  runApp(MaterialApp(
    theme: customTheme,
    home: MyApp(),
  ));
}