Individual Styling for Menu Links

I have a pediatrics site that I am building and I think I’ve hit a wall. I’ve done as much Googling as I can and will continue but it would be great if someone here has already run through this. I need to style the menu so each link has a rounded box. The hard part is I need for each link to have a different BG color and on hover change to another color. I have been messing with the CSS Class option under the menu options but nothing takes. Does anyone know a good plugin for doing this or a rough Idea on where to start coding this? you can view the site here at Casa Alegre | Just another WordPress site Thank You!