<el-tooltip class="item" effect="dark" content="分享" placement="left" popper-class="draw_share_atooltip">
     <el-button>
      <div class="iconfont icon-_share"></div>
     </el-button> 
</el-tooltip>

//箭头颜色
.el-tooltip__popper[x-placement^=left] .popper__arrow::after {

   border-left-color: #515b62;

  }

.el-tooltip__popper[x-placement^=left] .popper__arrow{

 border-left-color: #515b62;

}

//背景颜色
.draw_share_atooltip{
   background: #515b62 !important;
 }