如何在Flutter中更改CupertinoNavigationBar中后退按钮的颜色

dependencies:
  flutter:
    sdk: flutter
  cupertino_icons: ^1.0.2

import 'package:flutter/cupertino.dart';

class CustomTheme {
  static final ThemeData themeData = ThemeData(
    cupertinoOverrideTheme: CupertinoThemeData(
      primaryColor: CupertinoColors.systemBlue, // 设置导航栏的主题颜色
    ),
  );
}

import 'package:flutter/material.dart';
import 'package:flutter/cupertino.dart';
import 'theme.dart';

void main() {
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: CustomTheme.themeData, // 应用自定义主题
      home: MyHomePage(),
    );
  }
}

class MyHomePage extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return CupertinoPageScaffold(
      navigationBar: CupertinoNavigationBar(
        leading: CupertinoNavigationBarBackButton(
          color: CupertinoColors.white, // 设置后退按钮的颜色
        ),
        middle: Text('Home'),
      ),
      child: Center(
        child: Text('Hello, World!'),
      ),
    );
  }
}