title: Flutter Extend ThemeData, add colours etc
body: <p>I am trying to extend the color scheme used by my first app. I created a separate file that contains the following:</p>
  <pre><code>import 'package:flutter/cupertino.dart';
  
  class Testy extends CupertinoThemeData {
    final Color bgws = Color.fromRGBO(120, 120, 120, 1);
  }
  </code></pre>
  <p>I then imported it into Main.Dart but cannot see how to use my new color. I thought <code>Testy.bgws</code> would do it but clearly I am missing something.</p>