A flamingo gets it's pinkish or orange color from the food it eats.
Picture from Otts World
Most flamingos we see are pink and that's because shrimp and other crustaceans are one of the primary sources of food. They also eat algae, diatoms, and aquatic insects. Flamingos that eat mostly algae are more deeply colored than birds that eat the small animals that feed off of algae.
AA flamThe flamingo’s pink or orange color comes from the food they eat, including algae, diatoms, and small aquatic insects and crustaceans such as shrimp. - See more at: http://animals.sandiegozoo.org/animals/flamingo#sthash.caDIBVzq.dpuf