Out of the box the control highlights a selected item with a light blue border. I can't see where this is coming from, and I'd like to make the styling a bit more emphatic.
I compared a selected and unselected node in the dom, and they look basically the same:

在框外，该控件用浅蓝色边框突出显示选定的项。我看不出这是从哪里来的，我想让造型更强调一点。我比较了DOM中选中和未选中的节点，它们看起来基本相同：

Unselected node:

未选择的节点：

<div role="treeitem"
     class="p-treenode-content p-treenode-selectable"
     draggable="false"
     ng-reflect-ng-class="[object Object]"
     tabindex="0"
     aria-posinset="4"
     aria-selected="false"
     aria-label="Label1">...
</div>

Selected node:

所选节点：

<div role="treeitem"
     class="p-treenode-content p-treenode-selectable"
     draggable="false"
     ng-reflect-ng-class="[object Object]"
     tabindex="0"
     aria-posinset="5"
     aria-selected="false"
     aria-label="Label2">...
</div>

I'd expect the selected node to have a class added or some other attribute I can key off for CSS, but these look identical. I can definitely put something in to set the class, but that seems ugly and something p-tree should support out of the box. But I can't see anything in the generated HTML or the API description to tell me how to do it. Something is going on because it does have that blue border, but I can't see where it is coming from. Maybe ng-reflect-ng-class but not sure how I'd use that.

我希望选定的节点添加了一个类或其他一些我可以为css键入的属性，但它们看起来是一样的。我当然可以放入一些东西来设置这个类，但这看起来很难看，而且p-tree应该开箱即支持。但我在生成的HTML或API描述中看不到任何东西来告诉我如何做到这一点。发生了一些事情，因为它确实有那个蓝色边框，但我看不出它是从哪里来的。也许是NG-Reflect-NG-Class，但不确定我会如何使用它。

Ultimately I want a CSS selector that allows me to set the selected item to, for example, have a gray background.

最终，我想要一个CSS选择器，它允许我设置所选项目，例如，具有灰色背景。