Flamingos are actually born grey. Their vibrant pink color comes from the carotenoid pigments in the shrimp and algae they eat every day. If they stopped eating these, they would eventually turn white!

In the animal kingdom, looking good often requires a very specific diet. The flamingo is perhaps the world's best example of a "living makeover" driven entirely by what goes into its stomach.
Flamingo chicks are born with dull grey or white feathers. At birth, they don't have a single drop of pink on them. It takes about two to three years of steady eating before they achieve their famous tropical glow.
The secret ingredient is carotenoids. These are the same organic pigments that make carrots orange or tomatoes red.
For a flamingo, being "pretty in pink" is a sign of success. A bright pink flamingo tells the rest of the colony that it is healthy and very good at finding food. On the other hand, a pale or white flamingo is often sickly or malnourished.
A flamingo's color isn't a permanent trait; it's a temporary dye job provided by nature. If you were to take a flamingo out of the wild and feed it something else, its vibrant pink would slowly fade away with every new feather that grows.