View file application/modules/Core/widgets/admin-menu-logo/index.tpl

<?php
/**
 * SocialEngine
 *
 * @category   Application_Core
 * @package    Core
 * @copyright  Copyright 2006-2020 Webligo Developments
 * @license    http://www.socialengine.com/license/
 * @version    $Id: index.tpl 9747 2012-07-26 02:08:08Z john $
 * @author     John
 */
?>

<div id='global_header_logo'>
  <a href='<?php echo $this->url(array(), 'admin_default', true) ?>'>
  <?php if(!empty($_COOKIE['adminmode_theme']) && $_COOKIE['adminmode_theme'] == 'dark'):?>
      <?php echo $this->htmlImage($this->layout()->staticBaseUrl . 'application/modules/Core/externals/images/logo-light.png', $this->translate('SocialEngine Control Panel')) ?>
    <?php else: ?>
      <?php echo $this->htmlImage($this->layout()->staticBaseUrl . 'application/modules/Core/externals/images/logo.png', $this->translate('SocialEngine Control Panel')) ?>
    <?php endif; ?>
  </a>
</div>