face2005,
<!DOCTYPE html>
<html>
<head>
<title>Untitled</title>
<meta charset="utf-8">
<style type="text/css">
span{
color: red;
}
</style>
</head>
<body>
<div class="frm_opt_container">
<div class="frm_radio">
<label for="field_omiiy-0">
<input type="radio" name="item_meta[45]" id="field_omiiy-0" value="Для жизни" > Для жизни
</label>
</div>
<div class="frm_radio">
<label for="field_omiiy-1">
<input type="radio" name="item_meta[45]" id="field_omiiy-1" value="Как инвестицию" > Как инвестицию
</label>
</div>
</div>
<script>
document.querySelectorAll('.frm_opt_container label').forEach(label =>{
let span = document.createElement('SPAN');
label.childNodes.forEach(el => el.nodeType == 3 && span.append(el));
label.append(span);})
</script>
</body>
</html>