Aging Bald Eagle chicks by their increasing color

The different ages of the three Bald Eagle chicks recently hatched —the tv birds — is easy to see. The birds are on a Minnesota DNR live video feed, nest location local but unknown. The chicks were born, I believe, a day apart. All three are surviving, not always the case when a third chick hatches. Often that bird, smaller and weaker than its siblings, dies or is killed. The three in this nest look good. The feathering on the birds' backs: one is light, one is darker, the third is darkest. I'm assuming the increasing color is indicative of age. Find them via the DNR web site.