Why are nipples pink?

[Artemis_Tardis]

Why are our nipples pink-ish (or black, depending on skin colour)? Why can’t they be blue or green, for instance? Why ARE they coloured differently from our skin?

[Der_Trihs]

@demian_travis

Why are our nipples pink-ish (or black, depending on skin colour)? Why can’t they be blue or green, for instance?

Probably because we just never happened to evolve blue or green pigmentation for our skins. The same reason we don’t have blue or green hair but do have blue and green eyes; if a mutation for blue skin never happens to appear, then evolution can’t select for it.

@demian_travis

Why ARE they coloured differently from our skin?

Wikipedia mentions the hypothesis that they are colored in order to aid infants in finding them.

[njtt]

They are colored (or shaded) differently so baby can see them and find them. It seems to me that they are not really a different color, but the same color as the rest of your skin, only darker. Thus on people with pink skin - i.e., “white” people - they are a deeper pink.

[Mangosteen]

Years ago I met an Australian girl on the beach in Goa. Like many of the Western girls there, she was topless and had virtually no pigment in her nipples. The color of her areolas were almost identical to her skin color.

I told my friend that she had albino nipples.

[jiHymas]

Perhaps because the light/dark pattern makes the areolae look more like the eyes on a face?

Breast Crawl: A Scientific Overview

We are tempted to speculate that if a baby can appreciate her mother’s face, she can definitely see the areola and nipple (perceived as a dark spot on a lighter background). This is consistent with Illingworth (1987) stating that a newborn baby shows more interest in a black and white pattern than in a blank grey card. Perhaps that is the main reason why the areola is hyperpigmented. This is in sharp contrast to animal breasts / nipples. Does this point to a possibility that as compared to young animals, human babies may be also vision dependent in homing on to the nipple?

[jiHymas]

… and green or blue colours would be more difficult from an evolutionary perspective. The areolae are pigmented with melanin and melanocytes, according to some Australians:
[QUOTE=Some Australians]
The makeup of nipple-areolar skin, in terms of its melanin and melanocyte content has not previously been established. This histological information is required if pigmentation of the reconstructed nipple-areola is to be successful in post-mastectomy breast reconstruction. We describe examination of 200 parallel sections of nipple-areolar skin of 20 women using histochemical (Masson-Fontana) and immunohistochemical (Mel-5) techniques, evaluated using quantitative image analysis. The amount of melanin present per length of basement membrane was 2.14 times higher in areolar skin than breast skin. The ratio of melanocytes to keratinocytes was 1:9.7 in areolar skin vs. 1:14.7 in breast skin. We also describe a cell culture and skin construct method using autologous human serum without toxic growth promoting additives, which could be used in the clinical setting of nipple-areolar reconstruction.
[/quote]

… and the body already has plenty of those, so why invent something new?