Your navigation menu has a panel area devoted to it within the Design tool. See below on changing the look of your navigation menu.
1. Select the Design tool in the gray navigation bar. Under the Sitewide tab in the menu to the right of your website preview, select Navigation.
2. Use the options in the Text panel to change your font selection, text color, capitalization, character spacing, and alignment.
3. Select the green Save and Publish buttons to take any changes live!