I would like to put in my 2 cents worth
This is not meant to alarm or offend anyone but I feel that reading this thread can give a false sense of security that all iris color change is normal.
Generally, heterochromia (different iris color) is genetic and has no medical consequences, it is a just a special characteristic of that eye/person. However, there are cases where the change could be associated with certain congenital medical conditions. On the other hand, adults irises usually (always exception to the rule) don't change color overtime unless due to injury, certain eyedrop use, or a possible ocular or medical condition. This type of acquired heterochromia requires careful examination and thorough medical history check to ensure that the change is not due to a medical issue.
So my point is: If you ever sees a change in your eye iris color (acquired) and you mention that to your eye doctor, and the first and only thing he/she said "oh, don't worry about it, it's genetic" without investigating the eye carefully and probing into your medical history, I think it's time to change to another doctor
Yes, I think heterochromia is cool, but it should not just be admired, but be understood as well.