(There is a lot of debate related to this topic, but this is an article based more on the facts and a separate post will be about my opinions based on these facts.)
Designer Babies are children who have their human genome altered, or their genetic makeup created, by scientists to make sure the child has certain genes or not. Gene modification can allow alter the physical appearance of the baby such as influencing the eye color.
As an example following with eye color, brown eyes are a result of a large amount of melanin in the iris and blue eyes have very little melanin. The genes that determine that amount would be modified as such to give the desired eye color of the child.
Designer babies can also be protected from disease before they’re even born. Embryo screening allows doctors to diagnose diseases (ex. anemia) before the child is born and with this technology of changing the genetics, they child would be solved of this crisis and thus living a healthier life.