Some flowers also change color upon pollination, as a way to tell potential pollinators 'nope, don't need you here, pass on to the next flower please'. Kniphophia / Red Hot Pokers are famous for it, that's what gives them a nice color swatch from red to orange to yellow at the base of the blossoms.

As far as I know, MG do not change color when pollinated.

Color of MG blooms are affected by the air temps, seasons, and the height of the sun, IE angles not pollination.

Karen, I've had the same thing happen to my MG blooms, especially this year. The temps have been crazy, the humidity even crazier, and some days, it has been deadly humid in the morning and then dryer in the afternoon.
OR, it's been very sunny in the early AM, then all cloudy or the reverse.

the bloom colors have been very strange this year.

Fran