vue页面如何单独给背景色全方案

mounted(){
document.body.style.backgroundColor="#ffffff";
}

#app{
    position: absolute;
    height: 100%;
    width: 100%;
    top:0;
    left: 0;
    overflow-y: auto;
    background-color: #fff;//背景色为白色
  }

//进入路由时
beforeRouteEnter(to,from,next){
  window.document.body.style.backgroundColor='#fff'
  }
      //离开时
beforeRouteLeave(to,from,next){
    window.document.body.style.backgroundColor=''
  }

#app{
background-color:'#fff';
height: 100%;
position: fixed;
width: 100%;
}