Olá, respondendo ao desafio proposto na atividade, o meu stateful widget ficou assim:

        body: ListView(
          children: [
            Padding(
              padding: const EdgeInsets.all(8.0),
              child: Task(corRow1: Colors.black, corRow2: Colors.pinkAccent, corRow3: Colors.purple, widthContainer: 100,),
            ),
            Padding(
              padding: const EdgeInsets.all(8.0),
              child: Task(corRow1: Colors.redAccent, corRow2: Colors.greenAccent, corRow3: Colors.yellow, widthContainer: 100,),
            ),
            Padding(
              padding: const EdgeInsets.all(8.0),
              child: Task(corRow1: Colors.orange, corRow2: Colors.purple, corRow3: Colors.lightBlue, widthContainer: 100,),
            ),
            Padding(
              padding: const EdgeInsets.all(8.0),
              child: Task(corRow1: Colors.brown, corRow2: Colors.black45, corRow3: Colors.red, widthContainer: 100,),
            ),
          ],
        ),

a classe:

class Task extends StatelessWidget {
  final Color corRow1;
  final Color corRow2;
  final Color corRow3;
  final double widthContainer;
  const Task({required this.corRow1, required this.corRow2, required this.corRow3, required this.widthContainer, super.key});

  @override
  Widget build(BuildContext context) {
    return Padding(
      padding: const EdgeInsets.all(8.0),
      child: Row(
        mainAxisAlignment: MainAxisAlignment.start,
        crossAxisAlignment: CrossAxisAlignment.center,
        children: [
          Container(
            color: corRow1,
            width: widthContainer,
            height: 100,
          ),
          Container(
            color: corRow2,
            width: widthContainer,
            height: 100,
          ),
          Container(
            color: corRow3,
            width: widthContainer,
            height: 100,
          ),
        ],
      ),
    );
  }
}