title: Identifiying and coloring empty element in XSLT
body: <p>I have an address book, the XML for which is given by </p>
  
  <pre><code>&lt;addressbook&gt;
      &lt;entry&gt;
          &lt;name prefix="Mr."&gt;
              Zack Black&lt;/name&gt;
          &lt;address&gt;
              &lt;street&gt;101 Main St&lt;/street&gt;
              &lt;city&gt;Searcy&lt;/city&gt;
              &lt;state&gt;AR&lt;/state&gt;
              &lt;zip&gt;12345&lt;/zip&gt;
          &lt;/address&gt;
          &lt;phone location="home"
              number="501-279-9999" /&gt;
          &lt;phone location="work"
              number="501-279-1111" /&gt;
      &lt;/entry&gt;
      &lt;entry&gt;
          &lt;name&gt;John Brown&lt;/name&gt;
          &lt;phone number="501-305-2222" /&gt;
      &lt;/entry&gt;
      &lt;entry&gt;
          &lt;name&gt;Susan White&lt;/name&gt;
          &lt;address&gt;
              &lt;street&gt;2000 Center Rd&lt;/street&gt;
              &lt;city&gt;Dallas&lt;/city&gt;
              &lt;state&gt;TX&lt;/state&gt;
              &lt;zip&gt;67790&lt;/zip&gt;
          &lt;/address&gt;
          &lt;phone location="home"
              number="501-279-0000" /&gt;
      &lt;/entry&gt;
  &lt;/addressbook&gt;
  </code></pre>
  
  <p>Now, there are a few empty cells. I want to identify them and then color them using some particular color, say red. How can I do this?</p>