Have you ever heard of recessive genes? I would tell you to spend some time studying it, but you would just probably be introduced to more nonsense about evolutionary biology.
To make it simple, as others have also done:
My father had green eyes, my mom had brown eyes. I have blue eyes -having had two grandfathers with blue eyes, who each contributed a blue eyed gene. (My sister had green eyes, and my brother had brown eyes! So for me, I got the two recessive blues, one masked by my father's green eyes, and one masked by my mother's brown. In genetics, they call that bb, although it is actually much more complex than that, and many genes are technically involved.
My husband's father had brown eyes and his mom had green eyes. My husband has brown eyes, he has one siblings with blue eyes, another with brown, and one with green. So the same kind of thing - blue being recessive. So my husband could have had Bg or Bb - (B being dominant brown, and g being green).
So after 4 children, we are pretty convinced my husband is Bg. We had one child with very green eyes, and three brown eyes. I was kind of sad I had no blue eyed children.
But God is good! My one son married a blue eyed woman, and I have two blue-eyed grandchildren. Yes! And the other son married a woman with brown eyes, and we have a brown eyed grandchild, and another blue eyed and strawberry blond hair grandchild. We have no idea where the strawberry blonde hair came from. No one on either side of the family had that although there were a few light blondes and dirty blondes.
It is fascinating to think about all the potential genes that Adam and Eve had - both dominant and recessive. perhaps they were even polyploldal??