Highlighting parent page link while on child page

Do not edit the Twenty Thirteen theme. It is the current default WordPress theme and having access to an original, unedited, copy of the theme is vital in many situations. First create a child theme for your changes. Or install a custom CSS plugin.

I am using a child theme! That’s what I’m editing!

Try using Firefox with the Firebug add-on for this kind of CSS troubleshooting. Or use whatever developer tool is available in your web browser.

Firebug doesn’t seem to help. I’m stumped. Any other advice?

It tells you the classes you need to target by exposing the underlying HTML https://snag.gy/ABrpS.jpg (screenshot using chrome’s equivalent of firebug).

Do you know how to use CSS?

I do. I wasn’t too familiar with using Firebug. With Andrew’s advice, I inspected the element and tried targeting that specifically, but still nothing. There must be something I’m overlooking. I mean, Twenty Thirteen highlights parent menu items by default so I don’t know why it wouldn’t be acting in the same fashion.