I could be just tricks of lighting though. I don't think Firaxis would go out of their way to purposefully change the skin tone on an already existing character. It would fit perfectly well with all the lack of attention to detail that we've seen so far in the Leader Pass for them to have played with lighting without considering how that would make the characters look different from one another.
Just to provide some clues (and obviously increasing brightness on a 2D image isn't the same as digital lighting on a a 3d model), the picture below should give some indication of the effect of increasing the light a bit.
View attachment 647468
The beard is a different matter. It's larger and greyer, probably to make him look older.