Bridge discolored after 6 months. Any suggestions?

Dear renaen591, Unfortunately, once the
crowns are cemented, the only way to get them the color that you want is to
redo the crowns. Your dentist might suggest the color of your final
restorations, but ultimately, it’s your decision. Most often, the shade is
discussed at the time of the temporary crowns, so there is no misunderstanding
in what you want and like before the delivery of the final crowns.

The shade of a zirconia or any porcelain bridge should not change as long as it is polished.  An unpolished crown or bridge can collect staining a lot quicker an easier than polished porcelain.  The change can sometimes be attributed to exterior staining of the teeth from soda, tea, coffee, tobacco usage and certain foods.  I would return to your dentist and have him evaluate the situation and address your concern.  If the bridge needs polishing they may be able to take care of that in office.  If the bridge is off color then the only way to change this would be to replace the bridge.  The dentist should be able to show you the shade selection of the bridge and let you visually determine if the color matches the original shade of the bridge.