Colouring your irises is a cosmetic procedure for the upper class or the rich.  It’s Non-Schedule treatment and out of the reach of the average person, except as something they might save up for or a special gift.   

The colouring can be temporary – set to revert after a period of time, or permanent.  It’s a safe and simple procedure taking a couple of Tasks, but it does require highly specialised equipment so it’s not something you can do in the bathroom at home.  Colour choices vary, with a slightly enhanced or brighter version of a natural colour being common, though flamboyant types do occasionally choose unnatural colours, or mixed colours.

Ref:  F-343-Lia