It's just a slightly cool display and normal variation in the backlighting of these kinds of devices. Don't keep putting your device up next to others and you'll never notice it.
You should see the Motorola Xoom tablet I have at work- it looks fine on its own, but if I set it next to any of my iDevices, white looks like beige. It has a warm color cast. My iPod Touch 4G is also slightly warm, while my iPhone 4 is slightly cool like yours, as is my iPad. Your eyes even it out on their own, a kind of built in Auto White Balance.