What should the underside of your tongue look like?

Smooth wet colorful: The tissues of the floor of the mouth include glands/ducts, nerves, blood vessels and connective tissue with smooth cover of mucosa. The blood vessels are superficial, so purplish/blue is common. Fins of tissue (plica) are like ribbons near the ducts of the saliva glands. An oral anatomy textbook at your library can give great photos.

Pink: You will usually see color variations of pink under your tongue. Darker areas can appear blue, and those are often the veins that sit below your tongue. If you see anything that concerns you, see your dentist!