appbar 컬러 바꾸고 싶을 때 두가지 방법

# AppBar 속성바꾸기

appBar: AppBar(
	title: Text('AppBar'),
    backgroundColor: Colors.white, // appbar color.
    foregroundColor: Colors.black, // appbar text color.
   ),

# 테마 이용하기 

ThemeData(
    primaryColor: Colors.white,
    appBarTheme: const AppBarTheme(
      iconTheme: IconThemeData(color: Colors.blue),
      backgroundColor: Colors.white,
      foregroundColor: Colors.black,
    ),
  ),