Reduce header image height & menu color

I am looking for a way to reduce the height of the header image so the user doesn't have to scroll down to see that there is content below the header. I believe this is possible to do via the Additional CSS menu but am not sure what to input. My website is nr2003.jhodgedesign.com Also, how can I make the text of my menu items a different color when the user is on a page. For example when the user is on the Downloads page the menu text is pink. I'd like to change that color. Thanks!