<div class="container">
  <div class="arrow-up"></div>
  <div class="arrow-down"></div>
</div>

body{
  max-width:1000px;
}

.container{
  display:flex;
  justify-content:space-around;
  margin:10rem;
}


.arrow-up {
    width: 0; 
    height: 0; 
    border-left: 15px solid transparent;
    border-right: 15px solid transparent;
    border-bottom: 15px solid blue;
  }

 .arrow-down {
    width: 0; 
    height: 0; 
    border-left: 15px solid transparent;
    border-right: 15px solid transparent;
    border-top: 15px solid red;
  }