Dyed my hair for years, until the age of 30. Everything from blue, black, purple, fire engine red, mahogany, bleached white (not really dyed there). The best (at least for the hair) were definitely hennas. The worst was rit dye (fabric colouring). Naturally my hair is dirty dishwater with streaks of red (my beard used to grown in red). Since thirty, white/silver hairs started popping up where the red was, so I leave it as is.