The blue in the shadows is probably because that's what's there! Remember how the impressionist
painters scandalized the norm by actually putting blue in the shadows? Films can sometimes overreact. That's why corrective filters are needed. Portra 160, like I insinuated, is engineered to produce pleasing skintones under a variety of conditions, even if it is at the expense of correct reproduction of certain other hues. Portra 400 will probably be more realistic terms of landscape color, Ektar even moreso. Portra 160 is also much lower contrast to accomodate a wider range of illuminance and not accentuate things like skin blemishes, but therefore might come out looking
washed out and bland with respect to colors in nature. Just depends how you shoot. Might be good
insurance to practice with both and take both on the trip, though 160 would be more tolerant of
multiple airport X-rays.