I think you are talking about the way the "entry-title" classed <h*> tags are styled.
If you want them to appear in the same way the appear as links in an overview you will have to change the following files in your editor:
- content.php
- content-page.php
- content-single.php
And then use the same code for all titles:
<h2 class="entry-title"><a href="<?php the_permalink(); ?>" rel="bookmark"><?php the_title(); ?></a></h2>
At least you will have to use the same <h*> tag which usually is <h2>, not <h1>.
Note that adding the <a> anchor tag will mage a single content page link to itself. But that is no problem. Anyway you need the <a rel="bookmark"> to get the same CSS you desired.
