I can definitely see the difference now. The tail feathers stand up on the Leghorn a lot more too.
If you compare mine and readytogo's in the pic's, you might be able to tell without going home. They are very different tail feathers.
So I guess, depending on whether I have Leghorns or Rocks, obviously if they are leghorns the egg was one of the EE's, if not I have my fingers crossed this one will be a blue layer too.