Apple has introduced the notification center since the release of iOS 5.0. It was very warmly welcome thanks to the huge number of shortcuts. If you want to play around with the notification center, you can use NCColors app to customize the color.
NCColors is a new tweak which is available on Cydia. With this tweak, you can instantly change to color to red, blue, and green without having to reboot your idevices.
Your idevice must be jailbroken.