CSS underline on hover + active link in navigation and for hover in text body

Hi there, the only tricky thing here may be that my navigation text changes color depending on if you are on the homepage or another page. It goes from white on the homepage because it's over a full-bleed image to black on any other pages.

I would also like any links that I add to my About page or Journal to automatically be underlined when hovering. This is all black text.

Thank you so much! I am such a newbie and don't know much CSS. I have tried so many things thus far. **I am using the Camino template

share site url please?