I am tyring to fadeIn and fadeOut css background color with jquery ajax?

I am trying to fadeIn a background color in the beforeSend and fadeOut in the success with ajax. I don't know what I have done wrong. Help, please.

var data={
                              action: 'tag_user_update',
                                postSearchNonce : MyAjaxSearch.postSearchNonce,
                                                                tag : $(this).closest("a").text(),
                                                                users_id : $("#users_id").val()
                                                        }
                                                        $.ajax({
                                                                url: MyAjaxSearch.ajaxurl,
                                                                type:'POST',
                                                                cache: false,
                                                                data:data,
                                                    beforeSend: function() {
                                                                        $('.tag_link').animate({ backgroundColor:'yellow'},'slow');
                                                                                                          
                                                                                },
                                                                success: function(data){
                                                                          $('.tag_link').animate({ backgroundColor:'white'},'slow');
                                                                }
                                                                        });//ajax