Blacked out themes are pretty popular in custom Roms. They provide a unique look and feel while helping to save battery life. Some developers will black out Google apps but most don't blackout some of the most popular apps. Theme dev "B-Boy" has taken the liberty to theme Facebook and 6 other very popular apps. The apps are installable apk's. You will not need root to install these apps unless they are installed on your particular device as a system app. Not only is there an inverted Facebook app but there are versions with different colored text. Other inverted apps include Instagram, Skype, Pinterest, Spotify, KiK Messenger, and Whatsapp messenger.