What is the blue in Spirulina?

The liquid inside the cell is phycocyanin, a blue pigment present in only Spirulina. This pigment is a very powerful antioxidant found in Spirulina and is the primary source of its high protein and nutritional profile. Phycocyanin is a characteristic light blue color, absorbing orange and red light, particularly near 620 nm (depending on which specific type it is), and emits fluorescence at about 650 nm (also depending on which type it is). Phycocyanin is from the Greek phyco meaning “algae” and cyanin is from the English word “cyan”, which conventionally means a shade of blue-green (close to “aqua”) and is derived from the Greek “kyanos” which means a somewhat different color: “dark blue”.