how to change property with onPressed in flutter - flutter

Question

I am working on a flutter app and I wanted to change the color property(for each widget) to red when the user clicks on red and to green when the user clicks on the green. So any help?
this is the code of the widgets of the first page
cardItem(BuildContext context, int index){
return Padding(
padding: const EdgeInsets.all(5.0),
child: GestureDetector(
onTap: ()
{
SecondPage.name = "Question ${index +1}";
SecondPage.index = index;
Navigator.push(context, MaterialPageRoute(builder:
(context) => SecondPage()));
},
child: Card(
color: Colors.white,
child: ListTile(
title: Text('Question ${index +1 }'),
subtitle: Text('Yes or No'),
)
)
)
);
}
}
this is the code of the yes or no page
class _SecondPageState extends State<SecondPage> {
#override
Widget build(BuildContext context){
return Scaffold(
appBar: AppBar(
title: Text(SecondPage.name),
),
body: Center(
child:
Row(
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
Padding(
padding: EdgeInsets.only(right: 3),
child: FlatButton(
padding: EdgeInsets.all(15),
color: Colors.red,
child: Text('No', style: TextStyle(color: Colors.black),),
onPressed: () {
},
),
),
Padding(
padding: EdgeInsets.only(left: 3),
child: FlatButton(
padding: EdgeInsets.all(15),
color: Colors.green,
child: Text('Yes', style: TextStyle(color: Colors.black),),
onPressed: () {
},
),
),
],
),
)
);
}

Answer 1

Define a color variable Color color; inside your state and then give this color to all of your widget like button or whatever you have, And when user clicks on red inside the onPressed of your red button.
color =Colors.red;
setState(() { });
similarly, you can do this inside your green color button.

Answer 2

1). First declare a global variable like this,
var btnColor = Colors.green;
2). Now use this variable inside your widget like this,
color: btnColor,
3). Now use setState on button pressed to change the value of the Color
onPressed: () {
setState(() {
btnColor = Colors.red;
});
},
The value of color will change. This is called Stage-management you can
learn more about that