解决vant title-active-color与title-inactive-color不生效问题

import Vant from 'vant';
import 'vant/lib/index.css';
Vue.use(Vant);

 <van-dropdown-menu>
 <van-dropdown-item
  v-model="value"
 :options="developList"
 />
</van-dropdown-menu>
 
data () {
 return {
 value: ''
 developList: [
  {
  value: '1',
  text: '我是第一个'
  },
 {
  value: '2',
  text: '我是第二个'
  },
 ]
 }
}

<van-dropdown-menu>
 <van-dropdown-item
 title="请选择"
 v-model="value"
 :disabled="disabled"
 :options="developList"
 />
</van-dropdown-menu>
 
data () {
 return {
 value: ''
 developList: [
  {
  value: '1',
  text: '我是第一个'
  },
 {
  value: '2',
  text: '我是第二个'
  },
 ]
 }
}

<van-dropdown-menu>
 <van-dropdown-item
 :title="title"
 v-model="value"
 :disabled="disabled"
 :options="developList"
 />
</van-dropdown-menu>
 
data () {
 return {
 value: ''
 title:''请选择,
 developList: [
  {
  value: '1',
  text: '我是第一个'
  },
 {
  value: '2',
  text: '我是第二个'
  },
 ]
 }
}

<van-dropdown-menu>
 <van-dropdown-item
 :title="title"
 v-model="value"
 :options="developList"
 @change="changeDevelop"
 />
</van-dropdown-menu>
 
data () {
 return {
 value: ''
 title:''请选择,
 developList: [
  {
  value: '1',
  text: '我是第一个'
  },
 {
  value: '2',
  text: '我是第二个'
  },
 ]
 }
},
 
methods: {
 changeDevelop (i) {
 this.title = this.developList[i-1].text
 },
}

<template>
 <view>
 <demo-block title="基础用法" class="reset">
 <van-nav-bar title="标题" left-text="返回" right-text="按钮" left-arrow @clickLeft="onClickLeft" @clickRight="onClickRight" id="reset"/>
 </demo-block>

 <demo-block title="高级用法">
 <van-nav-bar title="标题" left-text="返回" left-arrow>
 <van-icon name="search" slot="right" custom-class="icon" />
 </van-nav-bar>
 </demo-block>

 </view>
</template>

<script>
 import Page from '../../common/page';

 export default {
 data() {
 return {

 }
 },
 onLoad() {},
 methods: {
 onClickLeft() {
 console.log("11");//TODO 进不来
 uni.showToast({
  title: '点击返回',
  icon: 'none'
 });
 },

 onClickRight() {
 uni.showToast({
  title: '点击按钮',
  icon: 'none'
 });
 }
 }
 }
</script>

<style>
 .icon {
 color: #1989fa;
 } 
 #reset /deep/ .van-ellipsis{
 color: red !important;
 }
</style>