Heterochromia means a difference in colour — either between the two eyes, or within one iris. It usually needs no treatment, and most people with it have no other eye or health problems.
Heterochromia
Each eye is a noticeably different overall colour from the other — most commonly present from birth and lifelong, occasionally acquired later.
Central heterochromia
One eye shows a distinct inner ring of colour around the pupil that differs from the rest of the iris — commonly a golden, amber or green ring within a browner or greyer outer iris.
Sectoral heterochromia
A distinct wedge or patch of different colour within one iris, rather than a full ring (central heterochromia) or a fully different second eye (complete heterochromia).
Heterochromia has several possible causes, most commonly present from birth with no other effect on eye health. This page describes the visual patterns only — it does not diagnose why any specific person's eyes look the way they do, and cannot rule in or out any particular cause.
A photograph — especially one taken with flash, in mixed lighting, or processed by phone software — is not reliable evidence of heterochromia. Reflections and white-balance shifts can make a single eye look a different colour in one shot without any real difference being present.
Heterochromia present since birth is usually lifelong and doesn't need treatment. A new or unexplained change in the colour of one eye — as opposed to a difference that's always been there — is different, and can be worth mentioning to an eye-care professional as a precaution.
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Source: American Academy of Ophthalmology. This page is general information, not medical advice — see an eye-care professional for any individual concern.