vue中鼠标移入字体下面显示颜色并改变字体颜色的问题

<template>  

<div class="smart_nav" :class="{'fixedTop':fixedTop}">

<!--<div class="smart_nav" :position':fixedHeight,'top':'top','zIndex':'zIndex'}">-->

<ul class="smart_nav_con">

<li class="fl smart_nav_right" :class="colorHover==0?'smart_index':'a_white'"><a class="white a_color" href="#smart_summarize" @mouseenter="spanHover(0)">产品概述</a></li>

<li class="fl smart_nav_right" :class="colorHover==1?'smart_index':'a_white'"><a href="#smart_advance" @mouseenter="spanHover(1)">产品优势</a></li>

<li class="fl smart_nav_right" :class="colorHover==2?'smart_index':'a_white'"><a href="#smart_help" @mouseenter="spanHover(2)">帮助文档</a></li>

<li class="fl" :class="colorHover==3?'smart_index':'a_white'"><a href="#smart_example" @mouseenter="spanHover(3)">客户案例</a></li>

<li class="span" :left':left}"></li>

</ul>

</div>

</template>

<script>

export default{

data(){

return{

left:0,

colorHover:0,

fixedTop:false,

// fixedHeight:'relative',

// top:0,

// zIndex:'0'

}

},

components:{

websiteHead,

websiteFoot,

goTop

},

methods:{

spanHover:function(index){

this.left = index *300 +'px';

this.colorHover=index;

},

needScroll:function(){

let scrollt=document.documentElement.scrollTop+document.body.scrollTop;

//console.log(scrollt)

if(scrollt>595){

this.fixedTop=true

}else{

this.fixedTop=false

}

// if(scrollt>595){

// this.fixedHeight='fixed';

// this.top=0;

// this.zIndex=10

// }else{

// this.fixedHeight='relative';

// this.top=0;

// this.zIndex=0

// }

}

}

,mounted(){

window.addEventListener('scroll', this.needScroll); //滚动事件监听

}

}

</script>

<style>

.smart_nav{

width:100%;

height:54px;

background:#414b5a;

position:relative;

}

.smart_nav_con{

width:1200px;

height:54px;

margin:0 auto;

font-size:14px;

color:#fff;

position: relative;

}

.smart_nav_con li{

width:300px;

text-align: center;

line-height:54px;

}

.smart_nav_con .smart_index .a_white{

color:#fff;

}

.smart_nav_con .smart_index .a_color{

color:#00a0e9;

}

.smart_nav_con li a{

color:#fff;

}

.smart_nav_con .smart_index a{

color:#00a0e9;

}

.smart_nav_con li{

line-height:54px;

}

/*蓝线*/

.smart_nav_con .span{

position:absolute;

bottom:0;

display:block;

width:36px;

border-bottom: 4px solid #00A0E9;

margin-left:128px;

transition:all 0.5s;

}

/*定位的样式*/

.fixedTop{

position: fixed;

left: 0;

top: 0;

z-index:2;

}

</style>