Out of my depth here on how WordPress works. I have a separate “blog” page and all my posts get tagged automatically in such a way that I can highlight the “blog” item on the menu. (WordPress knows “where the user is” and gives the menu items classes of “current-menu-item” and “current-menu-ancestor” etc., so you/the theme can style a menu item to be a different colour accordingly.)
Also pages get tagged in this way.
When the blog is on the main page, however, WordPress doesn’t seem to indicate “where the user is” for a random post. The only thing that I can think is that you could add them manually when you write the posts (via screen options), but that seems a bit Heath-Robinson.
Where is your blog? On the front page or a separate page? How would you define “where the user is” for a post accessed from the front page?
For pages, I note that if you make the pages “children” of a parent page (Edit a page > Page attribute > Parent > choose a page) then it picks up the classes in order to be coloured—maybe this is all you need…