Can you adjust the shade of veneers at cementation?

Unfortunately, it is not possible to darken the shade once they are cemented.  However, your dentist will usually do a try-in, a few minutes before he starts to cement them.  You should ask for a mirror during the try-in stage, so that you can double check the shade.  In the event that you are unhappy with the shade, you should say something prior to them being cemented.  Your dentist may have the ability to send them back to their lab and have the color changed at little or no cost.  However, once your veneers are cemented, your dentist will incur a much great cost to have them redone.  Good luck and I hope this helps. I'm an expert on veneers, so follow me if you have more questions.Sarah Thompson, DMDSoft Touch Dentistry

It depends, it is possible if the veneers are very thin and translucent. But the difference might not be very much. Have your dentist try on your veneers with different shades of try-in paste to give you a better idea how they will look after final cementation.

Your dentist should be able to show you and perhaps even try one on using a trial shading non-setting modifier. He/she can also use just water and try one or two on so you can see the finished result prior to final cementation. I'm sure the issue of opaqueness was handled and these should be naturally translucent.  Once you have o.k."d the appearance the veneers can be washed off, and treated for the bonding procedure using the shading protocol that you approved.