What is the best way to fix bleach stains?
Your carpet is now light tan, or used to be light tan?

Either way, the only thing I know of is to try to dye it back, and odds are, you're either going to dye more than you wanted (darkening the edges) or miss the edge ... either way, it's going to miss, and won't be 100% restored.

I'd consider rearranging the furniture (ie, hide it with a couch), or put a throw rug overtop if it's in the middle of the floor.

If it's in an area that's prone to issues, you can always replace just a section of the carpet with some other material -- at my mom's house we put some hardwood down just inside the back door where the cats liked trying to dig their way under a door, rather than replace the whole room.