If your veneers are porcelain, unfortunately ,we are not able to change the color of the veneers in the mouth once they are bonded to place. Your dentist should have given you a chance to approve the color before he bonded them to place. If he did so, and you gave your approval, then your only choice would be to have the veneers removed and replaced. It would be at his discretion to charge or not to charge. If he did not give you the chance to approve the color, then you have a better chance of negotiating with him to replace them at a lower price or for free. If you do decide to have them replaced, I would recommend first removing just one veneer and having the laboratory make it to the color that you want. The dentist should then try it on, and if you are satisfied and love it, you can proceed with having the other veneers removed and have them made to match the color of the new the veneer that you just approved. The one that was approved should he sent back to the lab so that it can be copied exactly in color. In this way you'll be sure that you get exactly what you want. If you are veneers are made of a resin or composite material, these can be changed in color by staining chair side if done properly. However changing the surface layer, the nearest will never have the Lester that the original veneers did. So most likely you would have to have these replaced also, but it would be easier to do so.