JSFiddle - React, Tailwind, and code Playground

HTML

<button onclick="onclickBut()">открыть</button> <span id="idSid" class="qw"> текст</span>

CSS

.qw {
color: aqua;
}
.xc{
color: red;
}

JavaScript

var idSid = document.getElementById('idSid');

function onclickBut() {
    idSid.className = (idSid.className == 'xc') ? '' : 'xc';
    localStorage.setItem('minbar', idSid.className);
}

if(localStorage.getItem('minbar') == 'xc') {
    document.getElementById('idSid').className = 'xc';
}