title: Theming sencha touch list
body: <p>I want to change the color of the headers in a grouped list. For the moment I've got the default theme. I think I have to use something like "$list-header-bg-color" but : </p>
  
  <ul>
  <li><p>WHERE can I use it ? I tried to write something like : </p>
  
  <p>$list-header-bg-color = '#CCC'</p></li>
  </ul>
  
  <p>directly at the end of the "sencha-touch.css" file but it doesn't work at all ... Somebody can explain me how does it works ? (with a little example please). Thanks in advance </p>