Use same horizontal rule from posts page on custom pages

Hi,

I am very new at this stuff. I have learned everything from researching forums like this and a lot of google searches. I always try to figure things out myself before asking for help but I am having a hard time finding the answer to this question.

I am using Twenty-Sixteen. My posts pages have rule below the site logo / main menu and above the blog post post. Here is an example of a post page:

https://sobervegan.com/?cat=4

In the Additional CSS I was able to make it green with:

.page-header {
border-top: 4px solid green !important;}

It acts as a nice separator but my custom pages do not have this separator. Here is an example of a custom page:

https://sobervegan.com/

I am trying to figure out how to add the same separator on the custom pages. Same size, width, and color so all the pages on the site look consistent. The normal HTML code is not working and my CSS knowledge is only as good as googling the things I have needed to change so far.

If anyone can help me out with some tips on how to accomplish my goal I would really appreciate it.

Thank you,
Scot

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