My friend has the white iPad and when we test videos (the exact same videos) bought through iTunes, my one has a sharper image while his colours seem slightly washed. We have the brightness set to the same level (around 75). I wonder if it's the white bezel around the screen that gives this impression, although I can't imagine why that would be.
I don't think there's any way to calibrate colour and contrast settings on the iPad other than brightness level.
I don't think there's any way to calibrate colour and contrast settings on the iPad other than brightness level.