ng-options如何实现其中某一项颜色为红色

Question

<select style="margin-right: 10px;float: none;margin-bottom: 0"
        ng-model="invInfo.invoice_id"
        ng-options="option.id as option.invType==2?option.invTitle+'(专票)':option.invTitle+'(普票)' for option in invoiceListData"
        ng-class="option.invType==2?'red':'yellow'">
</select>

这样写下来全是yellow,感觉是没有获取到option