I have read this comment on the website "...changing the DNA will not change the phenotypical effects that were caused by the code! So if you change somebody genes so that his eye colour would have been blue instead of brown it won't change for him, just his children. (The exception to this is stuff that constantly dies and gets renewed of course)" Now my question is: will changing the DNA change the hair structure/color taking into account the fact that it gets constantly renewed?
As best I can tell, the answer is probably, but not immediately. Hair is produced by hair follicles, and I believe that the color of the hair, caused by melanin, is coded into the follicle machinery. The lifespan of a human hair is generally between 3 and 7 years. It could conceivably take nearly a decade for all the hair on one's head to fall out. Until all hair present at the time of modification has fallen out, the portion of the hair shaft grown before modification will retain its original color. So it could take a decade before one's hair had entirely shifted to the new color.