title: Changing background color based on ng-class
body: <p>Hi In a table cell I am trying to change the background color based on the value using ng-class option </p>
  
  <pre><code>&lt;style&gt;
    .color-blue {
      background-color: blue;
    }
  
    .color-red {
      background-color: red;
    }
  
  &lt;/style&gt;
  
  &lt;td&gt;
    &lt;span ng-class="{'color-blue': r.no &gt; r.aNo,'color-red': r.no , r.aNo}"&gt;{{r.no-r.aNo}}&lt;/span&gt;
  &lt;/td&gt;
  </code></pre>
  
  <p>The values are all working fine. With <code>ng-class</code> option it is suppose to change the background color. But it displays values but no background color. </p>
  
  <p>Please let me know how to fix it so I can display background color based on positive or negative values.</p>
  
  <p>Thanks </p>