正如外部名称所暗示的那样，这些数字放置在元素外部，因此您无法通过li的背景色来影响它们。解决方法是在li中使用额外的div：

As the "outside" name suggests, the numbers are placed outside the element so you cannot affect them with li's background color. A workaround for this may be using an additional div inside the li:

<ol>
<li><div>Lorem ipsum dolor sit amet, consectetur ...</div></li>
<li><div>Some more text ...</div></li>
</ol>

然后为div添加以下CSS：

Then add the following CSS for the div:

ol li div  {
  width: 100%;
  height: 100%;
  background-color: #FFAAAA;
  margin-left: -20px;
  padding-left: 20px;
}

这会将div移动到数字的下方（即-20px值）和文本回到正确的地方（即20px的值）。

This will move the div to appear under the number (that's the -20px value) and the text in it back to the right place (that 20px value).