You can get some fabric dye in a similar color. It won't be a perfect match, but it may be close enough. Arts & Crafts stores usually carry this stuff, or you can search online. You could also have a professional carpet installer cut out the bad section and replace it with a new section - if you can still find it's match. If neither of the above works, you could always get an area rug to hide it, or you could bleach the rest of the carpet to make it match! Haha.

Good luck

Good one, cass.

Barring the above suggestions, see if you have some carpet in a closet that could be used to make the patch. Then a close match could be used to repair the closet. Call your carpet installer and see if that is feasible.