Was searching for something else when I happened across this post...
I managed to do this by trapping the following autocomplete events, and adding my own class into the outer that houses the autocomplete output. Then use CSS to format the elements as necessary. Hope this helps somebody.
$input.autocomplete({
focus : function(event, ui) {
$(".forms-search-result").parents("ul").addClass("myClass");
return false;
},
open : function(event, ui) {
$(".forms-search-result").parents("ul").addClass("myClass");
},
Example css:
.myClass a.ui-corner-all { font-weight:bold; }
Also as part of my JSON results, I simply pass back (from my JAVA AJAX Action) the HTML shell with the result embedded in it as part of the actual JSON "result". That way I can create elaborate HTML around each results, and then use the above method to format them the way I want.