There is more or less standard way of building Slideshows in drupal -- Views Slideshow module.

Module really works great and I would like to thank all people involved in it.

But what we should do when we want to change some of the behaviors of the javascripts of it? In my case the task was to change image style (imagecache preset) of the active page thumbnail. By default image style all thumbnails where grayscale, but we needed to make active thumbnail colorful. Like on screenshot image below.