If you want it done right, call a pro. 😊 If you want to go down the amateur rabbit hole instead, start by sitting down with a beer some quiet night, and you gotta go zen. This is a process. Here’s my monograph:
Maybe channel Ty Webb from Caddyshack: “I’m going to give you a little advice. There’s a force in the universe that makes things happen. And all you have to do is get in touch with it, stop thinking, let things happen, and be the ball.”
Now that your mind is limber, the most important thing is not to think of yourself as cleaning the stain. No, you need to have the attention to detail of a NASA inspector, the patience of a monk, and the creativity of an artist.
Before you jump into any sort of chemical processes like dissolving or surfactant actions, try to physically remove as much of the stain as possible without damaging the carpet or spreading the stain more. If wet, this means wicking or suction. If dry, then any sort of action like your scraping, picking, combing.
When as much has been physically removed as possible, start with a more mild solvent. For this, I’d try maybe rubbing alcohol or a non-acetone nail polish remover (ethyl acetate), which won’t melt the synthetic fibers of the carpet.
If the solvent is working to dissolve they dye and remove it from the carpet, remember that it’s still there in solution and must be wicked up to remove it. Use a very absorbent towel or paper towel, and change the absorbent material often to keep wicking effectively.
Go slow and observe carefully if the solvent is effective. Take care to be careful and not make it worse. If it’s not working, wick away the solvent or let it evaporate before trying something else.
Another solvent may be to try traditional ammonia based Windex. It’s weird but I’ve had great luck with Windex on a dirty grease on carpet.
It it worked to an extent, but you weren’t able to remove the stain completely, you might try a Bissell carpet cleaner at this point. Warm water and the cleaning solution scrubbed gently might loosen some more and vacuum it away.
Let it all dry. If it’s still there, you might try some big guns, but you’re now in the realm where you might do more harm than good. Some stronger solvents are old school stinky aerosol hairspray. There’s a crazy cocktail of chemicals in hairspray. I had a stain on a porous countertop that went away like magic with hairspray as the solvent. Might damage the carpet.
You could also try acetone which is literally nail polish remover (aka paint thinner), but that might harm the carpet.
If you get the stain mostly gone by scraping, solvents, and shampooing, but there are still some small spots or individuals strands of stained carpet, you can take the next drastic step of literally shaving a fraction of the top layer of the carpet strands (maybe a beard trimmer or a razor blade and a steady hand), or cutting out individual strands of carpet. I have done this, but you really need to go slow and then pause and assess, like trimming a bonsai tree. There’s no going back when you are physically cutting off part the carpet.
At the end, the final options are carpet shampooing with using an oxidizing bleach solution. Also if you can get strong sunlight to hit it directly, that can surprisingly neutralize the dye. I had a bright blue Thinking Putty that got smashed into a couch cushion at an Airbnb rental we stayed at, and after I got most of it removed, a final sit outside in strong sunlight did amazing things to remove most of the remainder.
All in all, if the carpet really matters and you can afford it, pay for a professional. I had a big white stain on my gray colored dashboard where my daughter “painted” with a titanium dioxide sunblock stick that I never could remove. I finally paid for a detailing at a dealership, and they had some magic secret to get it out beautifully so that it looked like new.