Cyanobacteria has a group of ancient Gram-negative, photosynthetic prokaryotes. Many botanists prefer cyanobacteria as a blue-green algae. The photosynthetic pigments present in the cell are chlorophyll, α,β carotene, myxoxantho phyll, myxoxanthin, C-phycocyanin and C-phycoerythrin. The C-phycocyanin is blue and C-phycoerythrin is red in colour. If C-phycocyanin is more as compared to C -phycoerythrin, it gives characteristic blue-green colour to the algae.