Answer
The pink/red color is probably due to a pigment in these cells which protect them from the UV radiation at high altitudes and latitudes.
Work Step by Step
UV damages DNA and cellular machinery, so cells need to be protected from it, especially when UV is intense as near the Poles and at high altitude. The pink/red pigment is probably not involved in photosynthesis itself since it is not a normal accessory pigment (see Concept 10.1), and no special form of photosynthesis is mentioned in the question to hint at such a role.
