The scientists at DisplayMate have tested the latest iPad mini's display and found it to be some of Apple's best work yet:
First of all, the colors and color accuracy of the iPad mini 4 now match all of the recent full size iPads and also the recent iPhones (5 and 6 including S and Plus). So across the entire mobile iOS product line you'll now see color matched photos and screen images. The mini 4 is an excellent super size upgrade to the iPhone 6(S) and Plus and now truly qualifies as a small version of the iPad Air 2.
But in terms of real-world viewing conditions, the record low 2.0% screen Reflectance actually makes a bigger visual difference for the image colors and image contrast that you actually see because ambient light washes out and degrades the displayed images and reduces screen readability - so its record low Reflectance actually makes a bigger difference!