What is causing my gum-line and above surrounding tissue to be gray above my crown, and how do I go about fixing it? (Photos)

Hi 
Given 6 years has passed, there will most likely be some gum recession.  The gum in this region is very thin and when exposed the underlying non-vital tooth structure can appear prominent in color even if it is only a millimeter.  If there is no pathology there may be options which do not require you to remove the crown.  Failing this removal of the crown, and a new crown respecting the biological width may be needed
Best Wishes
Dr S.Patel 

Hi:The grayness is most likely due to the root of the tooth darkening over time as a result of the root canal. The redness can be due to the margin of the crown being too close to the bone which results in a biological width issues.Best,Dr. Maddahi

It appears to be one of those challenges whereas the root of the problem is.. well, ironically.. the root of the tooth, based on info you provided. Plus you have a very high smile line that shows it all... And even though the tooth was internally bleached the color of the structure can still go back to darker shades. Making margins longer may not necessarily help since the is a limitation to as far as how deep one can extend the margins. In any case scenario it is hard to advice since the plan here would be dictated by a close up examination and consideration of all factors. Is there a metal post? Are the current crown margins flush and not causing any gum tissue irritation? I suggest to have a few independent doctors to look at it and provide you with multiple options