JSFiddle - React, Tailwind, and code Playground

HTML

<ul id="chocolates_suizos">
    <li>Blanco</li>
    <li>Con leche</li>
    <li>80% cacao</li>
    <li>Tres chocolates</li>
    <li>Barato</li>
    <li>Caro</li>
</ul>

CSS

#chocolates_suizos li {
    color: white;
    padding: 10px;
}

#chocolates_suizos li:nth-child(3n+1) {
    background: grey;
}
#chocolates_suizos li:nth-child(3n+2) {
    background: darkgrey;
}
#chocolates_suizos li:nth-child(3n+3) {
    background: dimgrey;
}