The coloring only targets gray hair and replaces it with subtle tones similar to your own natural color in 5. match in simple minutes. The ammonia-free formula lasts up to 6 weeks, Darkest Brow n gray hair color growth takes just five minutes as it targets and colors only gray hair, leaving your natural color intact. You won't get the dramatic color change you get with some women's hair colors. And once you apply, you're done. You can shampoo as often as you want and treat your hair the way you always want. Lasts up to six weeks or from haircut to haircut. Targets only gray hair and replaces it with subtle tones that match your own natural color in 5 easy minutes. Ammonia-free formula lasts up to 6 weeks until gray disappears.