Validation of radio button group using jQuery validation plugin

<input type="radio" name="myoptions" value="blue" class="required"> Blue<br />
<input type="radio" name="myoptions" value="red"> Red<br />
<input type="radio" name="myoptions" value="green"> Green

myRadioGroupName : {required :true}

You can also use this:
<fieldset>
<input type="checkbox" name="myoptions[]" value="blue"> Blue<br />
<input type="checkbox" name="myoptions[]" value="red"> Red<br />
<input type="checkbox" name="myoptions[]" value="green"> Green<br />
<label for="myoptions[]" class="error" style="display:none;">Please choose one.</label>
</fieldset>

and simply add this rule
rules: {
'myoptions[]':{ required:true }
}

'highlight': function (element, errorClass, validClass) {
            if($(element).attr('type') == 'radio'){
                $(element.form).find("input[type=radio]").each(function(which){
                    $(element.form).find("label[for=" + this.id + "]").addClass(errorClass);
                    $(this).addClass(errorClass);
                });
            } else {
                $(element.form).find("label[for=" + element.id + "]").addClass(errorClass);
                $(element).addClass(errorClass);
            }
        },
        'unhighlight': function (element, errorClass, validClass) {
            if($(element).attr('type') == 'radio'){
                $(element.form).find("input[type=radio]").each(function(which){
                    $(element.form).find("label[for=" + this.id + "]").removeClass(errorClass);
                    $(this).removeClass(errorClass);
                });
            }else {
                $(element.form).find("label[for=" + element.id + "]").removeClass(errorClass);
                $(element).removeClass(errorClass);
            }
        },