This uses flash but you can do it in HTML5 and with CSS if you want to. Changing the color when the mouse is hover is easy and the opening box under the link is not very hard. You could use JQuery to make your life easier: animation, fading, event are basic stuff with it.

About including it in WordPress I don't know it very well. I work with HTML standard in general but I think I can make it if the code isn't that messy.