In nature teeth are not the same color from top to bottom. They are usaully slightly more color saturated at the area near the gums and slightly lighter in the area away from the gums.
Most veneers can widen your smile. However, how much is dependent on a lot of things. You can have a wax up of the proposed veneers done on models of your teeth. This will serve as an architectural plan for your new smile. From this wax up you can have your dentist copy this plan with temporaries in your mouth so you can see what it would look like on you.
