You are looking for some way to make your character unique, some way to make him or her really stand apart from all of the other characters that have been created. Your search for just the right quirk to give your character has not been as successful as you would like.
Have you considered giving your character a strange way of caring for his/her hair? Do you have a character whose hair leaves a lot to be desired? Is your character losing his/her locks? Is a change of color needed? Is he/she really picky about the way he/she cares for his/her hair? You character refuses to use any of the modern ways of hair care and insists on using the ancient ways, or maybe some of the really unusual modern ways.
animal fat - Hair loss is a problem for both men and women. The ancient Greeks had a way to deal with this, though. Get the fat of some animals, make it into a paste, and slather it all over your head. This should make your hair grow. Question is, does your character really want his or her hair back that badly?
bull semen - Does your character have hair that isn't so healthy looking? Does it need to be moisturized? Does it need to be shinier? After all, everyone wants healthy looking hair. I can assure you that your character will be remembered if he/she uses this to treat their hair. This is actually in use today, so you can even use it yourself if you want. To moisturize the hair, make it shiny, and healthy, you need to condition it with bull semen. Before you freak out, this is mixed with other ingredients, but still. I really don't think that I will be using it. But your character could be a big fan of the conditioner containing this unusual ingredient.
blood of black cows - If you lived in the ancient world and wanted to change your hair to a darker color, what did you do? There wasn't a local Walmart to visit to buy a box of hair dye. Perhaps your hair stylist could dye your hair for you. That is possible, but he or she couldn't buy hair dye, either. Natural substances would have to be used. If you wanted to darken your hair and condition it at the same time, you would mix together henna, tadpoles, and the blood of black cows. This mixture would be applied liberally to the hair. Can you say yuck? Your character would definitely be a bit strange to use this to dye her hair. I really don't see a male character doing this, but who knows?
sulfur and safflower petals - During the time of Queen Elizabeth, all of the women wanted their hair to be red. So what if you were a natural blonde or brunette? Simple. You made up a powder of sulfur and safflower petals and applied this to your hair or your wigs. So what if it gave you frequent headaches, nosebleeds, and nausea, at least your hair would be red. If your character used this mix to color her hair red, why would she be doing so when she could just go buy some hair dye? Make sure her reason makes sense. You could also have a time travel story where she travels back to that time period.