Add class to empty Panels regions
The following works with all standard renderers (default/IPE).

There is no preprocess possibility for the regions, so some extra work is needed.

First add the following preprocess function to your template.php of your theme or your own module (change MY_THEME accordingly).

/**
 * Implements hook_preprocess_HOOK().
 */
function MY_THEME_preprocess_panels_pane(&amp;$vars) {
  // Determine if a panels panel (region) is empty.
  // Every pane needs to be checked for content.
  // Set the result on the panels display object.
  if (empty($vars['content']) || (isset($vars['pane']-&gt;IPE_empty) &amp;&amp; $vars['pane']-&gt;IPE_empty)) {
    if (!isset($vars['display']-&gt;panel_is_empty[$vars['pane']-&gt;panel]) || $vars['display']-&gt;panel_is_empty[$vars['pane']-&gt;panel] ) {
      $vars['display']-&gt;panel_is_empty[$vars['pane']-&gt;panel] = TRUE;
    }
  }
  else {
    $vars['display']-&gt;panels_is_empty[$vars['pane']-&gt;panel] = FALSE;
  }
}


Then you can use the data in the $display->panel_is_empty array in your PANELS-LAYOUT.tpl.php files to conditionally add extra classes. (Change 'PANEL' to the specific region.)

&lt;div class="panel-panel &lt;?php print !empty($display-&gt;panel_is_empty['PANEL']) ? 'panel-panel-empty' : ''?&gt;"&gt;
  &lt;?php print $content['PANEL']; ?&gt;
&lt;/div&gt;