Question: My dads eyes change colour sometimes. Like maybe at different times of the year. How does that work?

Paul Laurance-Young answered on 21 Nov 2019:

I’m not sure of you mean something like blue to brown?
If you mean ‘from dark brown to light brown’ then I may have an explanation: The is a pigment in your eye called melanin – the same pigment which makes some people darker skinned than others. Melanin gives your eyes colour (blue is absence of melanin) and the amounts of this protein dictate the colour of your eyes. Over time the amount of melanin may change (more or less) resulting in different eye colour. Also, as the iris expands and contracts in different light, this can stretch or compress the amount of pigment in the eye, giving the impression that eye colour is changing.