title: How to reference colour attribute in drawable?
body: <p>I would like to do a simple thing:
  Define a drawable which has exacly same background colour as system state-pressed background colour.
  I do it like this in res/drawables/my_drawable.xml:</p>
  
  <pre><code>&lt;?xml version="1.0" encoding="utf-8"?&gt;
    &lt;selector xmlns:android="http://schemas.android.com/apk/res/android" &gt;
      &lt;item android:state_selected="true"&gt;
        &lt;color android:color="?android:attr/colorPressedHighlight"/&gt;
      &lt;/item&gt;
      &lt;item android:state_selected="false"&gt;
        &lt;color android:color="@color/section_list_background"/&gt;
      &lt;/item&gt;    
    &lt;/selector&gt;
  </code></pre>
  
  <p>I always get:</p>
  
  <pre><code>java.lang.UnsupportedOperationException: Cant convert to color: type=0x2
  </code></pre>
  
  <p>Any clues?</p>
  
  <p>Regards</p>