Dave Caolo on 52 Tiger:
Apple has trained us since 2007 that a non-black or grey menu bar means something. There’s a call waiting, an ongoing recording or an active hotspot connection. Now, in the case of Apple’s Mail, Calendar, Messages, Phone and Contacts, it’s blue just to be blue. Worse, it’s confusing, and I spent the first few days erroneously thinking I had an active call or something in the background that I wasn’t aware of.
I don’t really know what Apple’s rationale was for the change either, but thankfully it seems everything is still consistent on the iPad.