How to change the appBar back button color

You can also set leading icon color globally for the app

MaterialApp(
  theme: ThemeData(
    appBarTheme: AppBarTheme(
      iconTheme: IconThemeData(
        color: Colors.green
      )
    )
  )
)

It seemed to be easier to just create a new button and add color to it, heres how i did it for anyone wondering

Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        leading: BackButton(
            color: Colors.black
        ),

You have to use the iconTheme property from the AppBar , like this:

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

Or if you want to handle the back button by yourself.

appBar: AppBar(
  leading: IconButton(
    icon: Icon(Icons.arrow_back, color: Colors.black),
    onPressed: () => Navigator.of(context).pop(),
  ), 
  title: Text("Sample"),
  centerTitle: true,
),

Even better, only if you want to change the color of the back button.

appBar: AppBar(
  leading: BackButton(
     color: Colors.black
   ), 
  title: Text("Sample"),
  centerTitle: true,
),

you can also override the default back arrow with a widget of your choice, via 'leading':

leading: new IconButton(
  icon: new Icon(Icons.arrow_back, color: Colors.orange),
  onPressed: () => Navigator.of(context).pop(),
), 

all the AppBar widget does is provide a default 'leading' widget if it's not set.