Why does the hair color of some babies change when they get older?

Genetics: As the baby grows, various genes get activated while others may get inactivated. It's the change in the millions of gene activation/inactivation that leads to changes as the baby matures. It is natural and is part of natural growth.

Normal: Newborns often can lose their whole head of hair (due to decreasing hormones)- but don't worry- it will grow back. And when it does it may be a different color, texture, etc. This is all normal.