I am on a yahoo message board for heterochromia iridium, and get e-mail digests. Today someone's post included some interesting tidbits about the condition. Did you know there is a Heterochromia holiday? Neither did I! Unfortunately we just missed it. Of course, they'll make a "holiday" for anything, but maybe it would be a good way to make Lucy feel special!
There is also a children's book about a little girl with two different colored eyes - one eye "the color of root beer while the other as blue as a lake." Sounds familiar. The book is about a girl who uses her special eyes to look for the (sometimes hidden) beauty in everyday things. It sounds like a nice story for any child!