highlight search field by having the focus

I would like that when I click on a field in the table and this field appears in the table search, this search engine will be highlighted in some way, changing the color for example

"initComplete": function (settings, json) {//Hace una busqueda haciendo click sobre el campo
                var api = this.api();
                api.$('td').not(" :nth-child(1),:nth-child(7), :nth-child(9)").click(function () {
                    $( ".input" ).css( "border", "3px solid red" );
                    api.search(this.innerHTML).draw();
                });
            },