She looks like she has that spray on tan. She is naturally very fair.
I know she is naturally a dark blonde. When you put a lot of highlights in your hair like this, you can look washed out with flashed photos. To prevent that wash out look in photos, they either put more color with makeup, tanning products, or a combo of both. Xtina does both to pull off the platinum hair look. Xtina is fair too naturally.
I would say she is a NC 30 with the tanning products. Usually these women have makeup artists that don't use just one level, they will use as much as three levels to give the illusion of a stronger jaw bone, straighter nose, high cheek bones and it will not have those tale signs of streaks from shadings from contour colors. It's all carefully blended foundation colors.