Answers for "how to set color of button in flutter hex code"

how to change the color of the back button in app bar flutter

appBar: AppBar(
  iconTheme: IconThemeData(
    color: Colors.black, //change your color here
  ),
  title: Text("Sample"),
  centerTitle: true,
),

flutter hex color

Color myHexColor = Color(0xff123456) 

// her you notice I use the 0xff and that is opacity or transparency of the color 
// and you can also change these value .