JSFiddle - React, Tailwind, and code Playground

HTML

<section>
<div></div>
<div></div>
<div></div>
</section>

CSS

section {display: flex}
div {height: 34px;}
div:nth-of-type(1), div:nth-of-type(3) {
  width: 34px;
}
div:nth-of-type(1) {background:red;}
div:nth-of-type(2) {background:green;flex-grow:1}
div:nth-of-type(3) {background:blue;}