On the subject of ostentatious hair colouring, Emil Kirkegaard has some thoughts:

For those not into memes: the idea is that poisonous animals advertise their dangerousness by [using] bright colours to scare away predators. Humans appear to do the same, as those who are poisonous — mentally ill — colour their hair in bright, dangerous-looking colours. Since this meme was made in about 2014, we’ve seen a strong increase in the number of people with unnatural hair colours. In the same time, we have seen a rise in mental illness in left-wingers…

Is unnatural hair colour associated with mental illness, or are we being misled by a few prominent people with this hair style who appear very mentally ill? We decided to find out using the venerable OKCupid dataset.

Charts and number-crunching ensue.

The full paper – Blue Hair and the Blues: Dying Your Hair Unnatural Colours is Associated with Depression – can be downloaded here.