Can a 70 year old not have grey hair?

Yes, a 70 year old can not have grey hair, though it is uncommon, as graying is largely genetic and varies widely between individuals and ethnic groups. Hair turns grey when melanocytes in hair follicles stop producing melanin pigment, and timing of this is controlled by genetics, with some people graying in their 20s and others maintaining natural color into their 70s and even 80s. Studies show about 75 percent of people between 65 and 79 have significant grey hair, but about 10 to 15 percent still have mostly original color, especially people with darker hair and certain ethnic backgrounds like Asian and African descent who gray later than Caucasian. Factors that delay graying include good genetics, low stress, good nutrition with adequate vitamin B12, copper, and protein, and absence of certain autoimmune conditions like vitiligo that affect pigment. Some 70 year olds dye hair to cover grey, so natural color may be hidden. Medical conditions like premature graying are linked to early loss of pigment, while delayed graying can be familial. Biblical view in Proverbs honors grey hair as crown of glory representing wisdom, but not having grey hair at 70 does not indicate poor health, it may indicate good melanocyte longevity. So yes, it is possible and normal for 70 year old to have little or no grey hair, though less common, and is usually genetic luck rather than sign of disease.