Actually i'm looking at a little merle girl right now, she is a very light fawn and is 4 weeks and already her merle spots are going away. So she should be sold as a pet only I think.
Make sure you breeder doesn't breed merles - I heard yesterday how someone bought a puppy and specifically asked if there were any merles in the background as she didnt' want one and guess what - they told her it didn't and it has. Unfortunately there would be a stigma attached to you if you bought one (which wan't a merle) but came from a merle breeder.
If you need any advice on what to ask etc. give me a ring.