In ancient times, six karyatides (singular: Καρυάτις, plural: Καρυάτιδες) graced the south column gallery on the Erechtheion (Ἐρέχθειον). The Erechtheion served as a temple to Athena Polias, Poseidon, the hero Erichthonius, and perhaps the legendary king Erechtheus. A karyatis is a support column of a temple, in the form of a woman. While the six on the Erechtheion appear copies, they can, in fact, be distinguished from one another. That is exactly what we'll be looking at today.

The statues are labeled Kore (maiden) A to F. Kore's A through C hold their left leg out, while Kore'sm D through F hold their right leg out. The biggest differences between the karyatides can be found in their clothing, and in their hair. While all six of the women wear an Ionic chiton, subtle differences can be found in its design. Kore B, for example, has a much shallower fold of cloth at her midsection, and their necklines all vary. Needless to say, they also have different bits missing, but as that was not intended by the sculptor, we'll not look into those differences today.
Their hair is most telling, though. Most have fishtail braids down the back, along with regular braids wrapped around the head, but some of the karyatides have sidecurls, while others do not, and their placement differs. o investigate this, Dr. Katherine Schwab created the Caryatid Hairstyling Project at Fairfield University, which laboured to recreate the hairstyles of the six karyatides from the Erechthion. The hairstyles were recreated on models--students in this case--by hairstylist Milexy Torres. You can see the results, and the subtle differences, below:
"The project was an experiment to replicate the hairstyles of the famous Caryatids from the Erechtheion [...] The Caryatids’ hairstyles are a remarkable and fascinating way to learn more about ancient Athenian society, especially during the fifth century B.C. [...] When Milexy made the final version, an adaptation of the general hairstyle, it was extremely comfortable, very light and cool.  I was surprised by how few pins and small plastic bands were needed to keep the different braids in place. "
The six statues currently on display on the Erechtheion are copies; five of the statues were removed during restoration of the building, and are now on in the Acropolis Museum in Athens where they are being restored and preserved. The last of the statues is in the British Museum in London, where it was taken to around 1800 by Lord Elgin. Despite steps to reclaim the statue, the British government has this far refused to return it. As a result, one of the pedestals in the display chamber of the statues in the Acropolis museum remains empty.