simple html coding to underline links or change their color?

Embarrassingly basic html question.

My theme does not underline links or change their color in the sidebar (until the cursor hovers over it).

I’d like to insert some code in the sidebar.php file to tell it to either underline links, or make them a different color from the standard text, or both, all the time–not just when the cursor hovers. Can’t remember what that code would be.

Can anyone remind me?

Thanks,
kwc