Removing a seciton of blue in the header

Hi everyone! We are trying to do something that sounds really simple, but doesn’t seem to be that simple. We want to remove this blue part in our template and cannot figure out how. We have been in the css file and the php and are not sure how to do it.

Here is the site live so you can see what we are talking about:
https://lawpsychologyethics.com/blog/

Any help is appreciated.