Frequently referred to as blue-green algae, cyanobacteria are photosynthetic and can manufacture their own food. However, though cyanobacteria resemble algae in many ways, they are prokaryotic and are classified with other bacteria in the kingdom Monera. The characteristic blue-green color they are known for is a result of a combination of chlorophyll and the blue pigment phycobilin. Yet, some species may contain additional pigments and may appear in various other colors, such as black, brown, yellow, and red.