how to change primary color in flutter code example

Example 1: how to give your app background colour in flutter

import 'package:flutter/material.dart';

void main() => runApp(MyApp());

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Welcome to Flutter',
      home: Scaffold(
        backgroundColor: Color(0xff00BCD1),
        appBar: AppBar(
          title: Text('Flutter Screen Background Color Example'),
        ),
        body: Center(child: Body()),
      ),
    );
  }
}

/// This is the stateless widget that the main application instantiates.
class Body extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Text('How Are You?');
  }
}

Example 2: scaffold theme flutter

MaterialApp(
  title: title,
  theme: ThemeData(
    // Define the default brightness and colors.
    brightness: Brightness.dark,
    primaryColor: Colors.lightBlue[800],
    accentColor: Colors.cyan[600],

    // Define the default font family.
    fontFamily: 'Georgia',

    // Define the default TextTheme. Use this to specify the default
    // text styling for headlines, titles, bodies of text, and more.
    textTheme: TextTheme(
      headline1: TextStyle(fontSize: 72.0, fontWeight: FontWeight.bold),
      headline6: TextStyle(fontSize: 36.0, fontStyle: FontStyle.italic),
      bodyText2: TextStyle(fontSize: 14.0, fontFamily: 'Hind'),
    ),
  )
);

Example 3: background color flutter

backgroundColor: Colors.white