While I would recommend greys in a lot of situations, I don't think your sister's family is looking for a grey. They fit all the requirements, but I think you guys are looking for a more "joie de vivre" type of dog.

I'm still pulling for that Aussie/ACD boy at the Lake County shelter I've been seeing him on craigslist and it really breaks my heart because he's SO pretty. I don't know how he is temperament wise though. That'll probably warrant a call to the shelter.