SOURCE

<div class='e' >

<div class='one'>
</div></div>

.hover {
  border: 1px solid #ccc;
  width: 120px;
  height: 120px;
  line-height: 20px;
  position: relative;
  top: 123px;
  left: 65px;
}
.e{position:relative;}
.one {
  border-style: solid;
  border-width: 25px;
  width: 0px;
  height: 0px;
  border-color: transparent;
  border-top-color: red;
}

.one:after {
  position: absolute;
  top: 12px;
  left:0px;
  width:0px;
  height:0px;
  border-style: solid;
  border-width: 25px;
  border-top-color: blue
}