Why are my veneers turning out the wrong shade/color? (photos)

The final shade of your veneers can be affected by the thickness of the veneer, the type of material the ceramist uses, the color of the tooth under as well as the cement.  Photos of the teeth before, without the veneers on and with the veneer trying are useful for the ceramist.  Photography as well as shade taking devices can be used.Before taking more tooth structure off, the lab can mask out the translucency inside of the veneers.  I do not like the look of opaque cements unless I have tried all other options to cover up the darker tooth under.

When doing veneers the underneath natural tooth color can show thru the porcelain there by creating a stained look... we need to block out these discolorations so we don't see showing thru. The dentist and lab tech work closely together to achieve a beautiful color without discolorations

Trial & Error should be avoided with veneers as it can result in unnecessary surface tooth loss. You can try a different cement, but it is also possible that as you age the dentin and remaining enamel of your tooth is changing color. I would seek a second opinion from another dentist who specializes in porcelain veneers, just to make sure and that there is nothing wrong with the tooth in question. Best of luck.