How To Change Formtextfield Label Text Color In Flutter

import 'package:flutter/material.dart';

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

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      debugShowCheckedModeBanner: false,
      home: Scaffold(
        appBar: AppBar(
          centerTitle: true,
          backgroundColor: Colors.indigo,
          title: Text('Change Lable Text Color'),
        ),
        body: Center(
          child: Padding(
            padding: const EdgeInsets.all(8.0),
            child: Theme(
              data: new ThemeData(
                primaryColor: Colors.green,
                primaryColorDark: Colors.red,
              ),
              child: new TextField(
                decoration: new InputDecoration(
                    border: new OutlineInputBorder(
                        borderSide: new BorderSide(color: Colors.teal)),
                    labelText: 'Enter UserName',
                    prefixIcon: const Icon(
                      Icons.person,
                      color: Colors.green,
                    ),
                    prefixText: ' ',
                    suffixText: 'USD',
                    suffixStyle: const TextStyle(color: Colors.green)),
              ),
            )),
          ),
        ),
    );
  }
}