Re: [DIYbio] Biohacking gray hair

Andreas, It's trivial to dye hair, but the color adjustment is limited by the existing color; it's like mixing extra pigment into existing paint.

Taking color out of hair is very challenging. Using high PH to deform the structure of the hair, expose the interior, and oxidise the natural pigments is standard practice. Black eumelanin is the least stable, though brown eumelanin is harder to attack, and red and yellow pheomelanins are always present and much more chemically stable. As the pheomelanins are typically more stable than the surrounding hair, the best result a dark haired person can expect from a hair bleaching is a bright brassy color, some hair damage, and minor chemical burns to the skin. 

Typically, the hair is allowed to recover for some amount of time with mildly acidic washes and deep conditioning. From there, blue is typically mixed into the hair to result in a more neutral grey, then the hair is dyed the desired color on top of that.

The process takes a significant amount of time, can fail catastrophically, doesn't work for all hair and skin types, and needs regular touching up when the roots grow in.