JSFiddle - React, Tailwind, and code Playground

HTML

<ul>
    <li>item1</li>
    <li>item2</li>
    <li>item3</li>
    <li>item4</li>
    <li>item5</li>
    <li>item6</li>
</ul>

CSS

ul {
    display: flex;
    flex-wrap: wrap;
    justify-content: space-between;
}
ul li {
    width: 48%;
}
ul>*:nth-child(4n+1), ul>*:nth-child(4n) {
  background-color: yellow
}
ul>*:nth-child(4n+2), ul>*:nth-child(4n+3) {
  background-color: green
}