I was comparing blank safari pages, the iPhone is a crisp white and the safari blank page on the mini is definitely yellowish.
I just posted a couple of photos on my blog showing the difference between the iPad mini and iPad 3:
http://www.mcelhearn.com/2012/11/04/color-differences-between-the-ipad-mini-and-the-ipad-3/
To me, when the two are side by side, there's a clear difference. When I'm using the iPad mini, however, it doesn't bother me.