How long does it take for a newborn baby to grow hair?

In my experience, my son was born w/curly, kinky, brown/black hair. A couple of days later, his hair turned VERY strait and dark brown... from there, he went to lighter brown, then red, then strawberry blond, to BLOND. Now he is 14yrs old, and dirty blond, like his dad :) Go figure..lol