I believe I read a psychological study on it or it was probably an example provided in the DSM-IV. Think: Bipolar Disorder, Borderline Personality Disorder, and Schizophrenia.
People with an unstable self-image and/or other mental health issues such as unhealthy impulsivity will dye their hair in unnatural colors. It's somewhere along the same lines as overt self-mutilation.
Because I’m really tired of reading that I somehow made this up, I’m not an expert or other dumb ass comments, I’ve taken the time to look for the study that I read. Here’s the 2013 study: “Changes in Appearance in the Presence of Major Stress Events” by Megan E. Stitz1 and John D. Pierce Jr.1
SAGE Open
April-June 2013: 1–8
© The Author(s) 2013
DOI: 10.1177/2158244013485093
http://sgo.sagepub.com 
