There is something called genes which determine the color of your eyes, your hair ... but in the eyes, for example, it works as follows, a person carries in their genes the information of their father and mother, call them A and B Well, if A carries brown information and B blue, you will have brown eyes, but your genes will have AB information, so if you have a child with a person who has AB or BB your children can be born with eyes blue or brown, the combinations being approximately 75% or 50% for brown