changing the style of yui treeview

In my project I make use of the YUI-TreeView widget. The CSS files of YUI are - let's say overwhelming. I found a nice description of how to find the correct style classes with Firebug. Here is an example where the developers explain how to obtain a folder style tree view.

I really just wanted to perform a small little change: The focus bg color of the selected tree nodes. This is what you have to override in your CSS:

.ygtvfocus{background-color:#B4CCFF;}