Step1: Add below style
<style>
.mystyle {
background-color: coral;
font-size: 25px;
color: green;
}
</style>
Step2: Add below javascript code
<script>
var ele = document.getElementById('ques29');
ele.setAttribute('class', 'mystyle');
</script></script>
Note: Here 'ques29' ID of HTML Control radio button. You can implement the same any HTML control.