I notice there hasn’t been any forthcoming responses to your, what seems to be a, simple question. I made a few calls expecting to get a quick answer and Geezzz….. ! Now I know why you haven't received any answers. The questions I received included, but weren’t limited to:
What color is the carpet?
What chemicals have been used to clean the carpet in the past?
Have you tried to stain a spot, and did it take the stain?
And on… and on…
Apparently bleach effects what happens next with fabric attributes also.
Anyhow… the typical distributors I thought would sell the dye to the public don’t, but there are quite a few “super-duper” remedies on-line if you search. I just don’t truly know if any of them will work correctly.
I think if I was sitting where you are, I would probably make a new stain in a closet somewhere out of sight. Spend a little time with RIT fabric dye from Walmart and mess around. You couldn’t really hurt anything hidden in the closet. I really do know this is a terrible answer, but the alternatives were scary and really expensive. Good Luck - Tom