How To Change Background Color Of Switch In Flutter App

import 'package:flutter/material.dart';

void main() => runApp(new MyApp());

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      debugShowCheckedModeBanner: false,
      home: MyHomePage(),
    );
  }
}
class MyHomePage extends StatefulWidget {
  @override
  State<StatefulWidget> createState() => MyHomePageState();
}

class MyHomePageState extends State<MyHomePage> {
  bool _isSwitched = true;
  List<Color> _colors = [
    Colors.teal, Colors.pink, Colors.orange, Colors.brown, Colors.black
  ];
  int _currentIndex = 1;
  _onChanged() {
    int _colorCount = _colors.length;
    setState(() {
      if (_currentIndex == _colorCount - 1) {
        _currentIndex = 0;
      } else {
        _currentIndex += 1;
      }
    });
  }
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        backgroundColor: Colors.amber[500],
        title: Text("Change Switch Color"),
      ),
      body: Column(
        children: <Widget>[
          Expanded(
            child: Center(
              child: Switch(
                onChanged: (val) => setState(() => _isSwitched = val),
                activeColor: _colors[_currentIndex],
                value: _isSwitched,
              ),
            ),
          ),
          Expanded(
            child: Center(
              child: RaisedButton(
                onPressed: _onChanged,
                child: Text("Change Color"),
                color: Colors.amber[500],
                textColor: Colors.white,
              ),
            ),
          ),
        ],
      ),
    );
  }
}