It may be a little bit of stain that can be removed at your next dental cleaning. In the meantime try these suggestions for removing tooth stain.
They don't look like cavities, but if you want to know for sure, ask your dentist to check them.
To know for sure, your dentist will need to dry them with air, look at them from every angle, and use an instrument to check for decay.
Most likely it's just a little bit of stain that can be polished off at your next cleaning. Stain can come from any food or liquid that has any color at all. Dark sodas can definitely stain your teeth. More importantly, sodas cause cavities. Diet soda is better but still very acidic and not good for your teeth.
Stain is more likely to occur between your teeth or in the deep grooves of your molars. Mild staining from food or liquid does not harm your teeth and can be easily removed at your next cleaning.