So, here is a confirmation of the color drifting of the portrait mode of the new gen iPhone. when a face is detected, the colors are being drifted. I am not going into the all detail here about the exact recipe apple is using, but the deltas are measurable … If you look carefully, the effort is mostly to boost blue and green, and its visual effect drives the picture to be less yellow. There is an additional processing done to avoid washing the yellows and lose yellowness on strong yellows.
No face:
Red(RGB in pic) 211 91 82
Blue 67 84 136
Green 69 101 62
Yellow: 237 209 110
With Face
Red 216 91 82
Blue 82 98 150
Green 93 133 76
Yellow 248 217 109
Again, this is quick and dirty look at something people seem to care, over all, the colors are there, a little modified, but nothing to be crazy about. I would be happy if Apple allows you to turn it off.