JSFiddle - React, Tailwind, and code Playground

HTML

<div class="first">
  <h1>test</h1>
  <h2>test 2</h2>
  <h3>test 3</h3>
</div>

<div class="second">
  <h1>test</h1>
  <h2>test 2</h2>
  <h3>test 3</h3>
</div>

CSS

h3:first-child{
  background: yellow;
}

.second > h3{
  background: yellow;
}