JSFiddle - React, Tailwind, and code Playground

HTML

<ul>
    <li id="current">1</li>
    <li class="item4">2</li>
    <li id="current" class="item4">3</li>
    </ul>

CSS

#current {color:red}
.item4 {color:green}
#current.item4 {color:blue}