Dental crown looks green. (photo)

From the blurry and limited view of your photo, I agree the metal underside is showing through. They grey hue is the metal.  I have no further info to go on- alt views or x-rays, but I suspect that you have bone loss and tissue (gum) loss in the area which makes the implant esthetics more challenging. With that in mind, there are other options for crowns that have color blocking centers that will hide that show through better. The darkness to either side is likely the gum loss and that is a more complicated problem.  Return to your original dentist to see what other options there might be for your case.
Again, the info you've supplied is very limited so its impossible to give a definitive answer.

Hi:I would definitley talk to your dentist about your concerns.  Please make sure the abutment under the crown is zirconium.  Most likely you have a metal abutment under the crown causing the color of the crown to be effected.Best,Dr. Maddahi

Hello,
With dental implant crowns many times it is possible to unscrew (if screw retained) or de-bond (if cemented with a weaker cement) and send back to the laboratory for shade modification without having to remake it. Call your dentist and have him/her look at it.
Dr. Mazaheri