Baby eye color genetics, explained
A baby's eye color comes from the amount and distribution of melanin in the iris, and it is shaped mainly by two genes, OCA2 and HERC2, which predict brown or blue. About eight other genes add shades like green and hazel. More melanin means browner eyes; less means blue. Because several genes are involved, eye color is a probability, not a simple prediction.
The pigment behind eye color
Eye color is really about pigment. The iris, the colored ring around the pupil, contains melanin, and the more eumelanin (a brown-black pigment) it holds, the darker the eye appears. High concentrations produce brown or dark brown eyes; low concentrations scatter light and read as blue. Green and hazel sit in between, with moderate pigment plus optical effects.
Which genes are involved
Two genes do most of the work. OCA2 and HERC2, located near each other on chromosome 15, are the strongest predictors of brown versus blue. Roughly eight additional genes fine-tune the outcome toward green, hazel, and everything between. Because so many genes contribute, eye color is polygenic, and any prediction is a statistical estimate drawn from population studies rather than a Mendelian certainty.
Why unexpected colors happen
Since eye color is not controlled by a single dominant-recessive gene, surprising combinations are possible. Two blue-eyed parents having a brown-eyed child is uncommon but not impossible, precisely because the trait depends on the interplay of several genes. That is why any calculator gives odds, not answers.
Newborn eyes keep changing
Even the color you see at birth is not final. Iris color in infants often shifts during the first 6 to 18 months as melanin gradually accumulates in the iris. A baby born with blue eyes may develop brown or hazel eyes by their second birthday, so an early guess can turn out quite differently within a year or two.
See a fun preview
Genetics gives you the odds; a predictor gives you a face to imagine. If you would like a playful preview of a possible child, you can blend both parents' photos and see a shareable result in minutes, just remember it is for fun, not a forecast.