SOURCE

   <div class="arrow"></div>

 .arrow {
     position: absolute; 
     top: 26px;
     left: 39px;
     width: 0px;
     height: 0px;
     border-top: 40px solid transparent;
     border-right: 40px solid #ccc;
     border-bottom: 40px solid transparent;
     border-left: 40px solid transparent;
 }
 
 .arrow::after {
     content: '';
     position: absolute; 
    
     border-top: 39px solid transparent;
     border-right: 39px solid #87cefa;
     border-bottom: 39px solid transparent;
     border-left: 39px solid transparent;
 }