Changing Color of Footer Menu in Oxygen Theme

I am WP Newbie and I just start to understand CSS Stylesheets.

Somehow I don’t find the right object to change when I try to change the text color of the footer menu in the Oxygen theme here.

As you can see the footer menu is not readable as I have switched to a black background. How the heck can I change the footer text to grey or white?

Firebug and custom CSS plugin is installed.
Thx in advance.