It's all in the eyes
A friend, Jenny, was asking if we thought Holly's eyes were going to stay blue so I thought I'd have a look back through my photos and see if I could find any of the boys at the same age. For reference, here is Holly, now, at 6 and half months:
As you can see their eyes are already darker and greyer than Holly's eyes. I don't have any shots of Mitch at the same age where you can really see his eye colour, but in this shot when he was about 9 months old you can kind of see his eyes are brown: and the shot below where he is 1 you can see they are definitely brown.
So who knows if Holly's eyes will stay blue, she will be a lucky girl if they do because dark hair and blue eyes can be quite striking!