Liz I am not sure when they change but I am pretty sure eye colour depends on grandparent's eye colour. My dad had brown eyes and my mum's are blue, so I carry one brown and one blue gene. DH's parents both have blue eyes, so he carries two blue genes. Brown is dominant, so if my egg has a brown gene our baby will have brown eyes (brown beats blue) but if my egg has my mum's blue gene our baby will have blue eyes.

What colour eyes does/did your DH's parents have?