JSFiddle - React, Tailwind, and code Playground

HTML

<div id="triangle-down"></div>

CSS

#triangle-down {
width: 0;
height: 0;
border-left: 50px solid transparent;
border-right: 50px solid transparent;
border-top: 100px solid red;   
position:relative;
}

#triangle-down:before{
    content:"";
    position:absolute;
    top:-103px;
    left:-55px;
    width: 0;
    height: 0;
    border-left: 55px solid transparent;
    border-right: 55px solid transparent;
    border-top: 110px solid blue;
    z-index:-1;
}