JSFiddle - React, Tailwind, and code Playground

HTML

<div id="wrapper">
  <div id="t-up-bg">
    <div id="tri-up">
    </div>
  </div>
</div>

CSS

#wrapper{
  position: relative;
  width: 105px;
  height: 105px;
}
#tri-up {
  position: absolute;
  top: 3px; left: -50px;
    width: 0;
    height: 0;
    border-left: 50px solid transparent;
    border-right: 50px solid transparent;
    border-bottom: 100px solid red;
}
#t-up-bg{
  position: absolute;
  top: 0; left: 0;
  width: 0;
    height: 0;
    border-left: 53px solid transparent;
    border-right: 53px solid transparent;
    border-bottom: 105px solid blue;    
}