SINCLAIR STAMMERS / Phase contrast photomicrograph of Blue green alga / Cyanobacteria (Spirulina platensis) each algal filament or Trichome is 5 microns in diameter.

Yva Momatiuk & John Eastcott / Arctic Fox (Alopex lagopus) in blue phase on coastal cliff, Saint Paul Island, Pribilof Islands, Alaska

Yva Momatiuk & John Eastcott / Arctic Fox (Alopex lagopus) pup in blue phase at entrance of burrow, Saint Paul Island, Pribilof Islands, Alaska

Fred Bavendam / Emperor Angelfish (Pomacanthus imperator) in its juvenile color phase, Bali, Indonesia

Constantinos Petrinos / Ribbon eel in male blue phase {Rhinomuraena quaesita} Sulawesi, Indonesia - species is hermaphrodite changing sex from male to female; juveniles are black, male is blue underneath , and final female p...

Heather Angel / Bloody bellflower (Nesocodon mauritianus), female phase with red nectar surrounding stigma. Native to Mauritius. Cultivated at Kew Gardens, London, England, UK.

David Fleetham / Bird wrasse (Gomphosus varius) male in terminal phase, Hawaii.

Linda Pitkin / Queen parrotfish (Scarus vetula), terminal phase - male, on coral reef. Bonaire, Leeward Antilles, Caribbean.

Terry Whittaker / Arctic fox (Alopex lagopus) female with blue colour morph winter coat walking along coast, Hornstrandir Nature Reserve, Iceland, April

Terry Whittaker / Arctic fox (Alopex lagopus) female showing blue colour morph, winter coat, scavenging in snow along the beach, Hornstrandir Nature Reserve, Iceland, April

Terry Whittaker / Arctic fox (Alopex lagopus) female showing blue colour morph, winter coat, walking on beach, Hornstrandir Nature Reserve, Iceland, April

Terry Whittaker / Arctic fox (Alopex lagopus) cub exploring away from the den, Hornvik, Hornstrandir, Westfjords, Iceland. July