JSFiddle - React, Tailwind, and code Playground

HTML

<div class="container">
  <div class="div1">
    black
  </div>
  <div class="div2">
    yellow
  </div>
</div>

CSS

.container{
  display:flex;
  flex-direction:row;
}
.container > div{
  flex: 1 1 auto;
  text-align:center;
}

.div1{
  background-color:black;
  color:yellow;
}
.div2{
  background-color:yellow;
  color:black;
}