A picture would help. Chances are it won't be a true butternut since it was grown from seed from a store bought squash. It's highly likely that the original squash was cross pollinated.

Rodney

It might make something usable. Let it grow as long as possible before harvesting them.

Leave them on the vine, if the vine is live and going. Chances are they might change color. But after the vine dies pick them and keep the in a place like a garage and see what happens.

Nothing else, you can cook them and see how they taste. Butternut squash is the sweetest squash/pumpkin that I know.