Change the color of the caption. You can also write you own style rules within the caption to acchieve this.

<div class="demo" id="container">
    <ul>
        <li>
            <a href="#"><img src="img/1.jpg" title="this is a normal caption" /></a>
        </li>
        <li>
            <a href="#" >
            <img src="img/2.jpg" title="<h3 style='color:yellow'>custom the caption</h3><hr/><p>with html, you can put link, button or any other element you want </p>" />
            </a>
        </li>
        ...
    </ul>
</div>

 $(function() {

     $('#container').sliphover({
         fontColor: '#d14'
     });
     
 })