解决，在点击分页之后或者其他地方之后，el-tree背景颜色没有了

:highlight-current="highlightBd"

 <el-tree
            :data="deptOptions"
            :props="defaultProps"
            :highlight-current="highlightBd"
            :expand-on-click-node="false"
            :filter-node-method="filterNode"
            ref="tree"
            @node-click="handleNodeClick"
          />

<style scoped lang='scss'>
/* 改变被点击节点背景颜色，字体颜色 */
::v-deep .el-tree-node:focus > .el-tree-node__content {
  background-color: #4186FF !important;
  color: #fff !important;
}
/*节点失焦时的背景颜色*/
::v-deep .el-tree--highlight-current .el-tree-node.is-current > .el-tree-node__content{
  background-color: #4186FF !important;
  color: #fff !important;
}
</style>