How the highlight feature works?

I have realised, the headings to the threads I have not read stays, highlighted in red and once it’s read it turns black. When new posts are added the heading gets highlighted again.
This is a nifty feature ,especially in sales section, to look at adds were new information may have been added.
But when I read a thread and use the back button in the iPhone to go back to the previous page, it kind off does a “undo” and the heading stays highlighted as if I have not visited that thread at all. I notice this “undo” situation happens in other scenarios too, like when I reply to a mail and then clicks the back button it appears like I have not replied at all. But the reply gets sent and it shows only when I return back to that page later.
Is there another way to return to previous page, like a button in the forum screen rather than the phone task bar, so the highlight and normal transition works as intended?

Thank you. So can I take it its like that?

When you hit the back button and the color stays red, hit the refresh button or hit “threads”. You should see it turn black. It’s not an undo- it’s more that you have hit the back button into an old page vs a new one that reflects the changes.

Though, in my experience, if you enter a thread, quickly scroll past only a few posts, and quickly exit before you reach the end of the thread, the forum hasn’t registered that you have “read” it and the color will stay red.

Thank you. This in one of most user friendly forums I have experienced. But some of the other forums I have seen have a dedicated back or previous button that usually shows the changes immediately without the need for a refresh.
This being in other aspects giving a superior user experience I thought maybe I am missing were the button is, or maybe because of my phone os or something.
Glad that is cleared. Thank you