Want to get rid of those lines around the header at the top of your page? You have to get into the HTML of your Blogger Minima Template. This tutorial taught me how.
*When you're editing your "Fonts & Colors" it may still ask you for a border color. This is not for the border around header at the top of the page - it is for the dotted lines that divide your posts and sidebar widgets. Deleting those lines is another process.