My toenail colour turns grey.. what should i do ?

Depends: If this is the only issue you have, you may address it by painting the nail. For good health - Have a diet rich in fresh vegetables, fruits, whole grains, milk and milk products, nuts, beans, legumes, lentils and small amounts of lean meats. Avoid saturated fats. Exercise at least 150 minutes/week and increase the intensity of exercise gradually. Do not use tobacco, alcohol, weed or street drugs in any form. Practice safe sex. Get HPV vaccine.

Fungal, Damage.: More than likely grey toenails are a consequence of either a fungal infection (microscopic mushroom) or the result of trauma to the nail (air under the nail). To remove all doubt have your toe examined by a specialist familiar with toenail infections and trauma.