I have this code:
You can't. CSS does not have any way to select the "parent element":
http://snook.ca/archives/html_and_css/css-parent-selectors
Would prefer not to use jQuery, but don't mind too much.
Use: http://jsfiddle.net/KHc6X/
$('.thumb_image_holder_orange > img').hover(function(){
$(this).parent().toggleClass('hover');
})