I played the panel lottery too many times back in 2012 when the iPad 3 was released and the one that I settled on had a warmer tint but it mostly even across the entire screen. I rejected several pink, green, and partly yellow ones.
Then iPad Air 2 is definitely cooler relative to my iPad 3. Some sites put their test samples around 7000Kelvin or so. My Retina MBP, which is calibrated to 6500K with my Spyder 4, is warmer when comparing the whites visually with my new iPad had right next to it. I had to return my first Air 2 due to a dead pixel and that panel was about the same color temperature in the middle of the screen. That panel for whatever reason had a slight cooler tint on the right and warmer tint on the left when held in portrait orientation. The 2nd panel was even across the screen, for the most part.