Faça como eu fiz: o retorno do Widget

import 'package:flutter/material.dart';

void main() {
  runApp(const MyApp1());
}

class MyApp1 extends StatelessWidget {
  const MyApp1({super.key});

  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: Scaffold(
        backgroundColor: Colors.white70,
        appBar: AppBar(
          leading: const Icon(Icons.add_task_outlined),
          title: Text('Flutter: primeiros passos'),
        ),
        body: ListView(
          children: [
            WidgetsAttaks(
              color1: Colors.white,
              color2: Colors.pinkAccent,
              color3: Colors.lightBlue,
            ),
            WidgetsAttaks(
              color1: Colors.pink,
              color2: Colors.deepPurple,
              color3: Colors.blueAccent,
            ),
            WidgetsAttaks(
              color1: Colors.redAccent,
              color2: Colors.yellowAccent,
              color3: Colors.lightBlue,
            ),
            WidgetsAttaks(
              color1: Colors.purpleAccent,
              color2: Colors.white,
              color3: Colors.green,
            ),
          ],
        ),
      ),
    );
  }
}

class WidgetsAttaks extends StatelessWidget {
  final Color color1;
  final Color color2;
  final Color color3;

  const WidgetsAttaks(
      {required this.color1,
      required this.color2,
      required this.color3,
      Key? key})
      : super(key: key);

  @override
  Widget build(BuildContext context) {
    return Padding(
      padding: const EdgeInsets.fromLTRB(8, 16, 0, 0),
      child: Row(
        crossAxisAlignment: CrossAxisAlignment.start,
        children: [
          WidgetContainer(color: color1),
          WidgetContainer(color: color2, icone: Icon(Icons.people)),
          WidgetContainer(color: color3),
        ],
      ),
    );
  }
}

class WidgetContainer extends StatelessWidget {
  final Color color;
  final Icon? icone;

  const WidgetContainer({this.icone, required this.color}) ;

  @override
  Widget build(BuildContext context) {
    return Container(

      decoration: BoxDecoration(
        border: Border.all(width: 5.0),
        borderRadius: BorderRadius.circular(20.0),
        color: color,
      ),

      width: 100,
      height: 150,
      child: icone,
    );
  }
}