Skin color is directly related to latitude. Darker skin means more melanin, which absorbs more light and protects against sunburns and thus skin cancer.

Eye color factors are less confidently known, but darker eyes generally have a better time in bright daylight.

Regarding those two, it’s also worth mentioning that the Inuit people don’t follow those patterns, as while they have less sunlight, they also have to deal with reflected light off the snow.

Hair texture is like eye color in that we’re only mostly confident, but tight curls also probably protect from the sun.

It’s also been posited that epicanthic folds might help against freezing winds, but there’s no real evidence for that.