Just for Men Shampoo-In Hair Colour targets only your grey hairs and replaces them with subtle tones that match your own natural hair colour. You will see perfect results in just 5 minutes, which last up to 6 weeks until the grey hairs grow out. Just for Men’s colour shampoo is quickly and easily applied and after it is complete you can shampoo as often as you like and treat your hair the way you always have. It is free from ammonia and leaves your hair in great condition once it is coloured.