OS X Yosemite features a dark mode option. If you turn this on, your menus, Dock and application switcher (the bezel that displays when you press Command-Tab) will be black, and not translucent.
To activate this, open System Preferences, then click on General. Check Use dark menu bar and Dock.
You can see above what the menus look like. I don’t find this very usable; the contrast is too harsh (it’s always harder reading light text on a dark background than the contrary), and many menu extras don’t display correctly, including some of Apple’s. But if you like this interface, it’s just a click away.