vue v-for出来的列表,如何实现点击某个li使得当前被点击的li字体变红

<template>
 <div class="person1">
  <div v-for="(item,index) in lists" @click="clickAdd(index)" :key="index" :class="{red:i === index}">
   <div>{{item.name}}</div>
  </div>
 </div>
</template>

<script>
export default {
 data () {
  return {
   isShow: false,
   i: null,
   lists: [
    {id: 1, name: 'rose'},
    {id: 2, name: 'mike'},
    {id: 3, name: 'jerry'}
   ]
  }
 },
 methods: {
  clickAdd (index) {
   console.log(index)
   this.i = index
  }
 },
 watch: {
 }
}
</script>

<style>
 li{
  list-style: none;
 }
 .red{
  color: red;
 }
</style>

<ul
 ref="seatTipOperation"
 v-if="seatTipOperationVisible"
>
 <li @click="handleSeatTipAdd()">添加</li>
 <li @click="handleSeatTipDelect()">删除</li>
 <li @click="handleSeatTipLock()">锁定</li>
 <li @click="handleSeatTipFillIn()">插空</li>
 <li @click="handleSeatTipSocket()">插座</li>
 <li @click="handleSeatTipSwop()">对调</li>
</ul>

handleSeatList () {
 this.seatTipOperationVisible = true
}

mounted () {
 // this的指向问题
 let that = this
 document.addEventListener('click', function (e) {
  // 这里that代表组件，this代表document
  // 冒泡也不会隐藏
  if(!that.$refs.seatTipOperation.contains(e.target)){
   that.seatTipOperationVisible = false
  }
 })
}