Sorry for the slow response, I’ve been away.
Yes, you should be able to filter the classes assigned with the ‘wp_nav_menu_objects’ filter. Examine the passed menu items array structure to determine how to access the assigned classes.
If you’re willing to create or alter a child theme (and not simply do this via plugin), a better approach is to locate the theme’s call to wp_nav_menu()
and add or overwrite a walker argument. Your walker will have complete control over the HTML created for all menu items, with the ability to apply quite complex logic to how it is created.
How do I get my anchor links to highlight when they are jumped to? Please help!
http://wordpress.org/support/topic/highlighting-anchor-page-jumps?replies=1