title: Not able to change TextField Border Color
body: <p>I am trying to change color of the border of my <code>TextField</code> using a <code>BorderSide</code>, but it does not work.</p>
  
  <p>This is my code below.</p>
  
  <pre class="lang-dart prettyprint-override"><code>new TextField(
    decoration: new InputDecoration(
      border: new OutlineInputBorder(
        borderSide: new BorderSide(color: Colors.teal)
      ),
      hintText: 'Tell us about yourself',
      helperText: 'Keep it short, this is just a demo.',
      labelText: 'Life story',
      prefixIcon: const Icon(Icons.person, color: Colors.green,),
      prefixText: ' ',
      suffixText: 'USD',
      suffixStyle: const TextStyle(color: Colors.green)),
    )
  )
  </code></pre>
  
  <p>Screenshot of the result is shown below.</p>
  
  <p><img src="https://i.stack.imgur.com/3i6vJ.png" width="380" height="838" /></p>