Can a permanently cemented implant crown be removed and replaced? What's the average cost of this procedure?

Just got dental implant & hate the color. I see a grayish shade in the middle of tooth. I told my dentist bout and he said he couldnt see it. Him & his staff made me feel like it was perfect. He asked me if i wanted permanent or temp cement. I said i was afraid it will fall off since its #10 so he did permanent. I see the grayish in it even more. He made me sign a paper that i was satisfied. Can crown be removed to change color after permanently cemented? What is the cost of this procedure?