mpvue更改小程序picker选中状态的颜色

<picker @change="bindPickerChange" :value="index" :range="array">
    <view class="picker" :class="index==0?'default':' '">
    	{{array[index]}} <i class="iconfont icon-xiala"></i>
    </view>
</picker>
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data () {
      return {
        index:0,
        array:[
          "请选择",
          "民生微实事",
          "志愿者服务活动",
          "其他意见建议"
        ]
	}
},
 methods:{
 	bindPickerChange(e){
   // console.log(e.target.value)
   this.index=e.target.value;
 }	

.picker{
     color:#333;
     }
 .default{
   color:#cccccc;
 }