When the scene goes over to William and his father, you will notice that the little boy playing William has blue eyes. If you were paying attention prior to the scene, you will notice that the older William has BROWN eyes!
People's eye color changes over the years. Many babies are born with blue eyes, but not that many keep the blue as they get older. I was born with brown, but they are now green.
Ok kim maybe people like you have their eyes change from brown to green which are not that different (in terms of eye color), but people can't change from blue to brown they are too different.
he could have had hazel eyes. my eyes are hazel and it a lot of things can make your eyes look different because they're a mix of blue/green/brown/AND gray. lighting, clothing, and even make-up can make the eyes appear different colors. i'm not saying that they ACTUALLY have hazel eyes, but this could be a legimiate excuse for the different colors.
Yes they can change from blue to brown! Look it up. Most babies are born with blue eyes, but eventually they change... even to brown. I do agree that this is a slipup though. Chances are... the director would have wanted the boy to resemble Heath Ledger as much as possible. Even at his young age, his eyes should be closer to the color they will remain in his adulthood.