O retorno do Widget

import 'package:flutter/material.dart';

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

class MyApp extends StatelessWidget {
  const MyApp({super.key});

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        colorScheme: ColorScheme.fromSeed(seedColor: Colors.blue),
        useMaterial3: true,
      ),
      home: MyAppBar(),
    );
  }
}

class MyAppBar extends StatelessWidget {
  const MyAppBar({super.key});

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        backgroundColor: Colors.redAccent,
        foregroundColor: Colors.white,
        title: const Text(
          'Flutter: Exercício',
          style: TextStyle(fontSize: 24),
        ),
        actions: <Widget>[
          IconButton(
            icon: const Icon(
              Icons.add,
              size: 30,
            ),
            onPressed: () {
              ScaffoldMessenger.of(context).showSnackBar(const SnackBar(
                  backgroundColor: Colors.red,
                  content: Text('Essa função ainda não está dísponivel :)',
                      style: TextStyle(fontSize: 18, color: Colors.white))));
            },
          ),
        ],
      ),
      body: Container(
        color: Color.fromARGB(255, 210, 220, 236),
        child: ListView(
          children: [
            Blocks(
                cor1: Colors.white,
                cor2: Colors.pinkAccent,
                cor3: Colors.lightBlueAccent),
            Blocks(
                cor1: Colors.pink,
                cor2: Colors.purple,
                cor3: Colors.purpleAccent),
            Blocks(
                cor1: Colors.pinkAccent,
                cor2: Colors.amber,
                cor3: Colors.lightBlue),
            Blocks(
                cor1: Colors.purpleAccent,
                cor2: Colors.white,
                cor3: Colors.green),
            Blocks(
                cor1: Colors.amberAccent,
                cor2: Colors.deepPurple,
                cor3: Colors.orangeAccent),
            Blocks(cor1: Colors.green, cor2: Colors.white, cor3: Colors.red),
          ],
        ),
      ),
    );
  }
}

class Blocks extends StatelessWidget {
  final Color cor1;
  final Color cor2;
  final Color cor3;

  const Blocks(
      {required this.cor1, required this.cor2, required this.cor3, super.key});

  @override
  Widget build(BuildContext context) {
    return Padding(
      padding: const EdgeInsets.all(8.0),
      child: Row(
        children: [
          Blocks2(cor1),
          Blocks2(cor2),
          Blocks2(cor3),
        ],
      ),
    );
  }
}

class Blocks2 extends StatelessWidget {
  final Color cor;

  const Blocks2(this.cor, {super.key});

  @override
  Widget build(BuildContext context) {
    return Container(
      width: 80,
      height: 120,
      decoration: BoxDecoration(
          color: cor,
          border: Border.all(
            color: Colors.black,
            width: 2,
          ),
          borderRadius: BorderRadius.circular(10)),
    );
  }
}
![Insira aqui a descrição dessa imagem para ajudar na acessibilidade](https://cdn1.gnarususercontent.com.br/1/1853972/be6f8f19-8bb5-4629-a9cd-16782b96802d.png)