Lightbox: changing the 'visited' color of the thumb (background-color block)

Lightbox v2.04
OS: WinXP Pro SP3
FF: 3.5.7
IE7

Hi,

I am trying to use lightbox, where the thumbnails are not smaller images but only blocks of background color.
When I don't use lightbox, I am able to control the color based on the state of the thumb (link/active/visited)...(thanks to the help of Wickham)
However with lighbox, the 'visited' attribute somehow gets ignored and the color remains as in '.projectthumbs li a' (hover/active works).

Is there any way to modify the script (css or js) to allow for the visited thumbs to change color?

HTML snippet
------------------------

<li class="projectthumbs">
   <ul>
      <li><a href='images/Cave Rock Blue.bmp' rel="lightbox" title="some caption"></a></li>
      <li><a href='images/Cave Rock Tan.bmp' rel="lightbox" title="some caption"></a></li>
      <li><a href='images/Cement.bmp' rel="lightbox" title="some caption"></a></li>
      <li><a href='images/Cemented Rock.bmp' rel="lightbox" title="some caption"></a></li>
   </ul>
  </li>

CSS snippet
------------------------

.projectthumbs li a{             
    padding: 0;
    color: #FFFFFF;
    background-color: #999999;
    width: 8px;
    height: 12px;
    padding: 0 2px;
    display: block;
}

.projectthumbs li a:link {
    background-color: #999999;
}
.projectthumbs li a:visited {
    background-color: #433e39; /*was #b82129;*/
}

.projectthumbs li a:hover, .projectthumbs li a:active {
    background-color: #b82129;
}

Thanks!