My iPhone 6 vs. my iPad Mini 4 vs. my two new iPhone 6Ss:
1. I have an iPhone 6 and iPad Mini 4. The photos on both devices are capturing true-to-life color and correct exposure in normal lighting (inside and outside).
2. On October 14th I purchased a new iPhone 6S from an Apple Store. Later I noticed the photo exposures/colors were off. Friends complained the exposure was wrong (colors are dark; no details in shadows).
3. On October 15th I took the iPhone 6S to the Apple Store. The tech agreed there was too much black in the shadows and greens were too dark. We used a Barnes & Noble STARBUCKS cup for whites, browns, and greens. The brown became dark chocolate and the green became dark olive. To test for a screen issue, images were opened on a Mac.
The Apple Store replaced the iPhone 6S without hesitation.
4. My new iPhone 6S is experiencing the exact same issues. Side by side my iPhone 6 and 6S do not take the same images as you can see from review sites.
This is not a screen, user (as the Apple tech would have to be an idiot too), or ‘Live Photo’ issue as some suggest.
Currently, aside for adjusting the brightness/contrast in a photo-editor, there is no fix.