The veins under my tongue are like a dark grayish color what can that indicate?

Veins under tongue: These veins are normal and indicate you are human! Some people have very prominent visible veins, others don't. Unless they hurt, or bleed, or do something else weird, don't worry about them.

Normal: Since veins carry unoxygenated blood they have a dark appearance and yours are most likely of normal color. If you still have concerns, see your physician for evaluation.

Normal: Veins carry blood that is depleted of oxygen and is therefore darker.