JSFiddle - React, Tailwind, and code Playground

HTML

<div class="caret"></div>
<p>
 border-color：red transparent transparent transparent;
 
</p>

CSS

.caret{
  height:0;/*将宽高都设置为0*/
  width:0;
  border:100px solid #000;
  border-color:red transparent transparent transparent;
}
p{color:red;}