Spanish Audio App (Error)

Error in material color in NumberAudio.dart

Error in import library of audiocache in HomePage.dart 

main.dart

import 'package:flutter/material.dart';

import 'HomePage.dart';

void main() => runApp(MyApp());

class MyApp extends StatelessWidget {

  @override

  Widget build(BuildContext context) {

    return MaterialApp(

      title: 'Spanish Number App',

      theme: ThemeData(

        primarySwatch: Colors.blue,

      ),

      home: HomePage(),

    );

  }

}

NumberAudio.dart

import 'package:flutter/material.dart';

import 'package:flutter/src/material/colors.dart';

class NumberAudio {

  String audioUri = "";

  MaterialColor buttonColor = Colors.black;

  String buttonText = "";

  NumberAudio(String aU, MaterialColor bC, String bT) {

    this.audioUri = aU;

    this.buttonColor = bC;

    this.buttonText = bT;

  }

}

HomePage.dart

import 'package:audioplayers/audioplayers.dart';

import 'package:flutter/cupertino.dart';

import 'package:flutter/material.dart';

import 'NumberAudio.dart';

import 'package:audioplayers/audio_cache.dart';

class HomePage extends StatefulWidget {

  const HomePage({Key? key}) : super(key: key);

  _HomePageState createState() => _HomePageState();

}

class _HomePageState extends State<HomePage> {

  AudioCache audioPlayer = AudioCache();

  List<NumberAudio> numberList = [

    NumberAudio('one.wav', Colors.red, 'one'),

    NumberAudio('two.wav', Colors.green, 'two'),

    NumberAudio('three.wav', Colors.blue, 'three'),

    NumberAudio('four.wav', Colors.pink, 'four'),

    NumberAudio('five.wav', Colors.yellow, 'five'),

    NumberAudio('six.wav', Colors.orange, 'six'),

    NumberAudio('seven.wav', Colors.teal, 'seven'),

    NumberAudio('eight.wav', Colors.brown, 'eight'),

    NumberAudio('nine.wav', Colors.purple, 'nine'),

    NumberAudio('ten.wav', Colors.blueGrey, 'ten'),

  ];

  play(String uri) {

    audioPlayer.play(uri);

  }

  @override

  Widget build(BuildContext context) {

    return Scaffold(

      appBar: AppBar(

        title: Text('Spanish Numbers'),

      ),

      body: Container(

        child: Center(

          child: Column(

            children: <Widget>[

              Image(

                image: AssetImage('images/logo.png'),

              ),

              Expanded(

                child: GridView.builder(

                  padding: EdgeInsets.all(10.0),

                  gridDelegate: SliverGridDelegateWithFixedCrossAxisCount(

                  crossAxisCount: 2, 

                  childAspectRatio: 2.0, 

                  crossAxisSpacing: 10.0, 

                  mainAxisSpacing: 10.0

                  ),

                  itemCount: numberList.length,

                  itemBuilder: (context, i) => SizedBox(

                    width: 100.0,

                    height: 50.0,

                    child: RaisedButton(

                      color: numberList[i].buttonColor,

                      child: Text(

                        numberList[i].buttonText,

                        style: TextStyle(

                          fontSize: 20.0,

                          color: Colors.white,

                        ),

                      ),

                      onPressed: () {

                        play(numberList[i].audioUri);

                      },

                    ),

                  ),

                ),

              ),

            ],

          ),

        ),

      ),

    );

  }

}