It can be redone within a few days.  you can request your dentist to do it for you. He will remove your old veneers, send it to the laboratory for rework on it till your are happy & satisfied.  Don't worry, your dentist will help you out.

veneers color cannot be changed. wait for some more time if still not satisfied you need to get them made again

Get your veneers redone.

Give it some time, getting use to something new takes time. Existing issues can take white veneers and make them seem less white-color of your tooth underneath, stained teeth can gray out veneers and even the glue/cement used to bond the veneers.

If you are not happy with the veneers, you will need to change the veneers. Because you can't change the colour once done..

The shade of the natural teeth or the veneers does differ in natural and artificial light..... also the shade selection is done by the dentist in concordance with the patient's opinion.... after the veneers have been placed, the only option if you are not satisfied with the result, is the replacement of the veneers..... Regards.....

dentist didn't show u before fixing ? Now nothing can be done if we try to remove them possibility of breakage . did u have highly discoloured teeth before ?