Exactly, that came to my mind too. Specifically, Harmattan's in-built apps came with color schemes for broad categories: blueish for communication, orangish for productivity, purplish for media etc.
It seems that Apple has already begun a similar and slightly more subtle approach in iOS 6 with their colored status bars. Communication apps (Messages, Contacts, Phone, Mail) have a blue status bar; Information apps (Safari, Weather, Stocks) have a black status bar. I could see Apple expanding upon this design premise to subdivide apps into their respective content areas like Harmattan.