Fluuter: Material3 App Bar shows no color, only white - flutter

Question

I am starting to use Material 3 for flutter.
However, even when use the basic counter app that is as default, when I add:
useMaterial3: true,
The app bar goes white, with no background. Even when I set : colorSchemeSeed
Here is my code:
// This widget is the root of your application.
#override
Widget build(BuildContext context) {
return MaterialApp(
title: 'Flutter Demo',
theme: ThemeData(
colorSchemeSeed: Colors.red,
useMaterial3: true,
),
home: const MyHomePage(title: 'Flutter Demo Home Page'),
);
}
Why does the app bar turn into a white background?
class _MyHomePageState extends State<MyHomePage> {
int _counter = 0;
void _incrementCounter() {
setState(() {
_counter++;
});
}
#override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text(widget.title),
),
body: Center(
child: Column(
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
const Text(
'You have pushed the button this many times:',
),
Text(
'$_counter',
style: Theme.of(context).textTheme.headlineMedium,
),
],
),
),
floatingActionButton: FloatingActionButton(
onPressed: _incrementCounter,
tooltip: 'Increment',
child: const Icon(Icons.add),
),
);
}
}

Answer 1

I'm not sure but if you can replace the colorSchemeSeed instead of primaryColor should work
// This widget is the root of your application.
#override
Widget build(BuildContext context) {
return MaterialApp(
title: 'Flutter Demo',
theme: ThemeData(
primaryColor: Colors.red,
useMaterial3: true,
),
home: const MyHomePage(title: 'Flutter Demo Home Page'),
);
}