izumov,
<!DOCTYPE html>
<html>
<head>
<title>Untitled</title>
<meta charset="utf-8">
<style type="text/css">
label{
display: flex;
flex-direction: column;
border: 1px solid hsla(0, 0%, 0%, 1);
width: 80px;
text-align: center;
}
label input{
text-align: left;
}
label:after{
content: var(--pp, "");
color: hsla(0, 100%, 50%, 1);
}
</style>
</head>
<body>
<label class="err"><input type="text"></label>
<script>
setTimeout(_=> {
const label = document.querySelector("label");
label.style.setProperty("--pp", '"Click me"');
}, 1000)
</script>
</body>
</html>