JSFiddle - React, Tailwind, and code Playground

HTML

<div class="wrapper">
  <div class="post">1</div>
  <div class="post">2</div>
  <div class="post">3</div>
  <div class="post">4</div>
  <div class="post">5</div>
  <div class="post">6</div>
  <div class="post">7</div>
  <div class="post">8</div>
</div>

CSS

.wrapper {
  width: 100%;
}

.post {
  text-align: center;
  line-height: 100px;
  margin: 2px;
  width: 40%;
  height: 100px;
  border: 1px solid #000;
  display: inline-block;
}

.post:nth-child(2n+1) {
  background: lightgreen;
}

.post:nth-child(2n) {
  background: lightblue;
}