"Discolored nails: Diabetes, stress, allergies and simple illness can cause your nails to appear discolored. A greenish nail color, however, can be a sign of infection, either in the nail bed or in your system.
Bluish nail beds can be a sign of lung trouble, such as emphysema or even asthma. A simple dark blue line in the nail can be a sign of skin cancer. Tiny black streaks can indicate a heart problem, while reddish-brown spots can indicate a deficiency of folic acid, protein or vitamin C.
List of Remedies for Nail Issues