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#compartilhando

Código feito

@override
  Widget build(BuildContext context) {
    const double lenght = 100;

    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        colorScheme: ColorScheme.fromSeed(seedColor: Colors.deepPurple),
        useMaterial3: true,
      ),
      home: Container(
          color: Colors.white,
          child: Container(
            color: Colors.black,
            child: Column(
              mainAxisAlignment: MainAxisAlignment.spaceEvenly,
              children: [
                Row(
                  mainAxisAlignment: MainAxisAlignment.spaceEvenly,
                  children: [
                    Container(
                      color: Colors.red,
                      width: lenght,
                      height: lenght,
                    ),
                    Container(
                      color: Colors.orange,
                      width: lenght,
                      height: lenght,
                    ),
                    Container(
                      color: Colors.yellow,
                      width: lenght,
                      height: lenght,
                    )
                  ],
                ),
                Row(
                  mainAxisAlignment: MainAxisAlignment.spaceEvenly,
                  children: [
                    Container(
                      color: Colors.green,
                      width: lenght,
                      height: lenght,
                    ),
                    Container(
                      color: Colors.lightBlueAccent,
                      width: lenght,
                      height: lenght,
                    ),
                    Container(
                      color: Colors.blue,
                      width: lenght,
                      height: lenght,
                    )
                  ],
                ),
                Row(
                  mainAxisAlignment: MainAxisAlignment.spaceEvenly,
                  children: [
                    Container(
                      color: Colors.purple,
                      width: lenght,
                      height: lenght,
                    ),
                    Container(
                      color: Colors.pinkAccent,
                      width: lenght,
                      height: lenght,
                    ),
                    Container(
                      color: Colors.white,
                      width: lenght,
                      height: lenght,
                    )
                  ],
                ),
              ],
            ),
          )),
    );
  }