title: Change color of checkbox field when checked
body: <p>I have a check box field with box label colored in green. I need to change the color of the boxlabel (say: yellow) when a user checks the checkbox. i tried validating the checkbox, but it doesnt work. Any suggestions?</p>
  
  <pre><code>xtype :  'checkbox',
  id: 'checkbox1',
  name : 'checkbox',
  style: 'background-color : #BCF5A9',
  boxLabel: 'Mycheckbox'
  //I tried the below handler function. but it doesnt work
  handler: function (checkbox, checked) {
              if (checked) {
                  style : 'background-color: #ddd';
              }
  }
  </code></pre>