<div id="mylist">
<div class="item"><span>1</span></div>
<div class="item"><span>2</span></div>
<div class="item"><span>3</span></div>
<div class="item"><span>4</span></div>
<div class="item"><span>5</span></div>
  </div>

.item {
  width:50%;
  margin-top: 10px;
  padding: 15px;
  background: #eaeaea;
  transition: background .3s;
}

.item.red{
  background: #D85442;
}

$("#mylist > .item").on("mouseover mouseout", function(){
    $("#mylist > .item").not(this).toggleClass("red");
});