Active Menu Items undefined? / Slogan-Definition overriden?

I love this theme - but there are two minor problems I can't quite manage for I'm not really experienced in CSS

1. I can't change the style of the active menu-items. The activated item has the color black but in the css-file there is not once metioned the color black (#000 or #000000): This is why I think that it is undefined. How and where can I define the color for the active item?

Example: http://www.axtimwal.de

2. No matter what I do, I can't change the slogan-properties, I think font-size and font-color of the slogan-block in the CSS-File are overriden by some other code. What can I do?

Thanks in advance,
Daniel