Radio field CSS Class

want to show the “radio filds option” differently for each radio field. but can’t use custom class becoz the custom class applied on input field, where as the text is in SPAN class, check this html code which is generated.

<label class="jet-form-builder__field-label for-radio">
<input type="radio" name="1com" class="jet-form-builder__field radio-field checkradio-field firstq" value="2" data-field-name="1com" data-switch="1">
<span>25-34</span>
</label>

now is it possible to add custom css to class “firstq”

thanks in advance