It is not possible with CSS, however you could do this with jQuery.
jQuery:
$('li').not(':hidden').last().addClass("red");
HTML:
<ul>
<li>Item 1</li>
<li>Item 2</li>
<li>Item 3</li>
<li class="hideme">Item 4</li>
</ul>
CSS:
.hideme {
display:none;
}
.red {
color: red;
}
jQuery (previous solution):
var $items = $($("li").get().reverse());
$items.each(function() {
if ($(this).css("display") != "none") {
$(this).addClass("red");
return false;
}
});