The negative influence of coffee on the teeth is not proven. Only if you drink hot coffee in cold weather while on the street. Due to the temperature difference, enamel may suffer. Drink only in its pure form, prepared from natural grains.
Coffee's other risks. Like any drink that isn't water, coffee can cause bacteria to grow in your mouth which can lead to tooth and enamel erosion. This can cause your teeth to become thin and brittle. Coffee can also cause bad breath, or halitosis, because it sticks to the tongue.
There are microscopic ridges and pits within the enamel of every tooth, and when you eat and drink, they can hold onto particles. That means that a dark drink like coffee could actually embed itself into your enamel, causing unsightly yellowing of the teeth.
Yellowed teeth is just discoloration and may not have any indication of the health of your teeth. If you brush, floss, rinse with a good mouthwash twice a day and see a dentist twice a year for a cleaning, you'll be fine. But if you drink coffee or tea daily, be prepared to have some slight discoloration of your teeth.