1` and `Topic2` to have font color red.

    <core-submenu icon="settings" label="Topics">
      <core-item label="Topic1"></core-item>
      <core-item label="Topic2"></core-item>
    </core-submenu>
    
@group Polymer Core Elements
@element core-submenu
@extends core-item
-->

<link rel="import" href="../core-item/core-item.html">
<link rel="import" href="../core-menu/core-menu.html">
<link rel="import" href="../core-collapse/core-collapse.html">

<polymer-element name="core-submenu" attributes="selected