Usually, the pink color on your eyes referred to as "pink eye", occurs due to a bacterial or viral infection of your conjunctiva. A virus is the most common pink eye cause in adults, while bacteria commonly affects children. It's common to get pink eye when you have a cold. An allergic reaction or irritants can also cause pink eye. Antibiotic eye drops can treat bacterial infections, but viral infections don't need treatment. Note that pink eye is prevalent among school children and is very contagious. See a doctor if symptoms don't start to improve within 12 to 24 hours.