Change dropdown menu style: background color for current page

Hi,
I’m trying to change the background of the section of a dropdown menu related to the current page.
In particular, I discovered that I need to edit the CSS section .dropdown-menu > .active > a from the CSS file bootstrap.min.css (line 5).
Is there a way to edit that section from the wordpress admin dashboard without accessing the file from the server where my website is hosted?
Thank you!