How can we change appbar background color in flutter

Declare your Color:

const primaryColor = Color(0xFF151026);

In the MaterialApp level (will change the AppBar Color in the whole app ) change primaryColor

return MaterialApp(
  title: 'Flutter Demo',
  theme: ThemeData(
   primaryColor: primaryColor,
   ),
  home: MyApp(),
);

and if you want to change it on the Widget level modify the backgroundColor

  appBar: AppBar(
    backgroundColor: primaryColor,
  ),