Text input decoration

main.dart

import 'package:flutter/material.dart';

final Color darkBlue = Color.fromARGB(255, 18, 32, 47);

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

var text = TextEditingController(text: 'HELLO');

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      theme: ThemeData.dark().copyWith(scaffoldBackgroundColor: darkBlue),
      debugShowCheckedModeBanner: false,
      home: Scaffold(
        body: Center(
          child: TextField(
            decoration: InputDecoration(fillColor: Colors.green, filled: true),
            controller: text,
          ),
        ),
      ),
    );
  }
}