I have an issue with using the Ambient CSS3 Menu add on. When I use it on the main content of the website, it has a blue background with white text. But when I add the menu to the sitewide headern nav block it becomes white text and white background.

I want to have a dark blue-ish background but it won't let me. I'm clicking the header nav block edit>design>background colour (changed it to blue). When I publish the edits it still is white text and white background.