Veneers can't mask my discolored tooth, what should I do?

Hi:In order to mask the color of the grey tooth, there has to be masking porcelian powder and opaquer cement used in the veneer.Best,Dr. Maddahi

Actually, the combination of internal bleaching and a veneer is the best option.  I'd try internal bleaching first and if that only helps some, then replace the veneer with a more opaque new one - and your doctor can prep the tooth a little differently to give more room to cover the tooth as well as put an opaque layer under it to mask out the black...  hang in there!