The timing, from the source

The clearest published answer comes from a paediatrician writing for the American Academy of Pediatrics, and it is refreshingly unwilling to guess: "New parents often ask what color I think the baby's eyes are going to be. I never answer this question until the child is at least 1 year old."

The reason is biological rather than coy. Eye colour is the appearance of the iris, and iris colour depends on melanin — the same pigment that determines hair and skin colour, made by cells called melanocytes. The AAP's explanation: if melanocytes secrete only a little melanin the eyes are blue; a bit more gives green or hazel; when they are busiest, brown, which is the most common eye colour worldwide.

And the timing follows from that: "Because it takes about a year for melanocytes to finish their work it can be a dicey business calling eye color before the baby's first birthday. The color change does slow down some after the first 6 months of life, but there can be plenty of change left at that point."

Why so many babies start blue

Newborn irises simply have not accumulated much pigment yet. The AAP describes the pattern in its account of how newborns look: "While many Caucasian newborns have blue eyes, this may change over the first year. If a baby's eyes are going to turn brown, they'll probably become 'muddy'-looking during the first six months. However, if they're still blue at that time, they'll probably remain this color."

The same page notes the important exception: "infants with dark-skinned heritage generally have brown eyes at birth, and tend to retain that color throughout life." So the "all babies are born with blue eyes" line that circulates online is simply wrong, and the AAP says so directly.

That muddy or hazel-looking in-between stage is the part that unsettles parents. It is pigment arriving unevenly, and it is not a sign of anything.

What genetics can and cannot tell you

The AAP is careful here: "Eye color is a genetic property, but it's not quite as cut-and-dried as you might have learned in biology class." Its list of tendencies, quoted rather than paraphrased because the hedging is the point:

Two blue-eyed parents are very likely to have a blue-eyed child, "but it won't happen every single time".
Two brown-eyed parents are likely, but not guaranteed, to have a child with brown eyes.
If one of the grandparents has blue eyes, the chances of a blue-eyed baby go up a bit.
If one parent has brown eyes and the other blue, the odds are about even.

Eye colour is influenced by several genes rather than one, which is why the single-gene square many of us were taught at school gives the wrong answer often enough to be useless for an individual baby. No published source gives reliable percentages for a specific family, so this page will not manufacture any.

The one pattern to mention

The AAP gives a single flag on eye colour itself: "If your child has one brown eye and one blue eye, bring it to your doctor's attention." Different-coloured irises, called heterochromia, can be benign but can also be associated with genetic conditions, so it is checked rather than assumed.

Two other colour changes are not about the iris at all, and are more urgent:

Yellow whites of the eyes. The AAP notes that jaundice may turn the sclera yellow. The NHS says jaundice usually appears at about two to three days old and fades within around ten days, but that a baby who develops jaundice in the first 24 hours should be checked by a health professional straight away. Jaundice that is still there after two weeks also needs review.
A white or cloudy pupil, including one that shows up white in a flash photograph. This is not an eye-colour question and should be looked at promptly.

What is actually checked, and when

The NHS's newborn physical examination, offered within 72 hours of birth and repeated at six to eight weeks, includes the eyes. NICE's postnatal care guideline NG194 sets out what that means in practice: the examiner checks for opacities, the red reflex, and the colour of the sclera. None of that is about predicting eye colour — it is looking for conditions like congenital cataract where early detection changes the outcome.

The HSE's eyesight timeline gives the useful developmental markers over the same period: focusing on a face or object from birth to six weeks; by six to eight weeks looking at you, following your face, smiling back and moving both eyes together; by around six months looking around with interest and seeing across a room.

What about eye colour predictors

Online calculators, including ours, work from parent and grandparent eye colour and give a probability, not an answer. They are a reasonable way to see the odds. They are not a substitute for waiting, and the AAP's own paediatrician declines to call it before a year for exactly this reason.

When to call

Speak to your midwife, health visitor, public health nurse or GP if:

Your baby has one brown eye and one blue eye.
A pupil looks white, cloudy or greyish, or shows up white in photographs.
The whites of the eyes look yellow, especially in the first 24 hours of life or after two weeks of age.
The eyes are not looking in the same direction all the time, or a drifting eye is still there after three to four months.
Your baby is not fixing on and following your face by six to eight weeks.
One eye looks larger or more prominent than the other, or your baby is very sensitive to light.

Call your local emergency number (999 in the UK and Ireland, 911 in the US and Canada, 000 in Australia, 111 in New Zealand) if your baby has a temperature of 38C (100.4F) or above or below 36C (96.8F), is unresponsive or unrousable, has a weak or abnormally high-pitched cry, looks pale, ashen, mottled or blue, is grunting or breathing over 60 breaths a minute, has a bulging fontanelle, or has a rash that does not fade under a pressed glass. Those are NICE's red flags for young babies, and they apply whatever colour your baby's eyes are turning.

What to let go of

There is nothing to do here, nothing to influence, and nothing that eye colour predicts about health, personality or anything else. Take the photographs, enjoy the muddy stage, and check again at a year.

When Do Babies' Eyes Change Colour