SOURCE

<div class=“big”>
<div class="div1"><div>
  </div>

.div1{
  width:0px;
  height：0px;
  margin:20px;
  background-color:green;
  border:3px solid currentcolor;
  border-color:transparent transparent transparent red;
  border-width:10px 10px;
  position:absolute;
  /* right:-10px; */
  top:50%;
  transform:translate(0,-50%);
}

.big{
  position:relative;
}

/* .div1::before{
  content:'';
  width:0;
  height:0;
  border:3px solid currentcolor;
  border-color: transparent currentColor transparent transparent;
} */