Every screen has a different colour temperature. I have never had a really good explanation...but they simply do vary. Some have theorised that there is more than one screen manufacturer. But I know for the iPhone 6S plus there is only one currently (characterised by a shadow screen blemish in the lower left corner on almost all samples) and the colour variance between them is crazy. So the bottom line is that it is a lottery. You could end up with a more blue one, or a more reddish one, or a more yellow one....or even worse, one that is yellow on one side and blue on the other. It is generally the case from what I have seen that the iPad pro is warmer than the iPhone 6S plus on average.