Within the structure of the 'verse, people travelling through time cannot take anything but their DNA with them--even fillings fall out of their teeth. So what would happen if a person had dyed hair? Would the dye come out when they travelled or does it somehow bond enough with the hair to remain in place? From what I can tell, only permanent hair colour gets inside the hair shaft, the rest sit on top of it, and bleach changes the structure of the hair. So I think bleach would stay in place and maybe permanent colour, but not the others?
Thoughts? Questions? Concerns?