The joint on their legs which looks like a backwards-bending knee is actually their ankle, and they are standing on their toes. Their knee is higher up close to their body and hidden in the feathers.
Flamingo chicks are white and get their colour from the pigment in the regurgitated so-called "crop milk" that their parents feed them. So while the chicks are turning pink, their parents' colour is fading.
Flamingos use their beak and tongue like a pump to suck food from the water that they have collected with their beaks.