Color of Emax crowns?

Following up on my previous post "Can you change the color of emax crowns" at my dentist request I am wearing the crowns with a temporary cement to see how I like them so as far as I'm concerned I haven't accepted the crowns yet. The "Staining" process that was mentioned in a previous response...How does that work? I really like the size and shape of the crowns but I'm not happy with the color shade!! My natural teeth are a little more yellowish/ beige than the crowns which seem greyish/white