jQuery move list item to end of list

I have this list that can be sorted with sortable. How can I move the li item with class .neutral to the end of the list when sorting is finished?

$(".thumbs").sortable({
    stop: function(event, ui) { 
        // move .neutral at the end of this list
    }
});

<ul class="thumbs">
    <li>red</li>
    <li>green</li>
    <li class="neutral">none</li>
    <li>yellow</li>
    <li>blue</li>
<ul>