My bro had a ‘roommate’ that managed to spill about 1/2 a bottle of fingernail polish on some short pile carpet.
Don’t know the makeup or ‘type’ of polish other than it’s red 
very red.
Any ideas about getting it out? Or is he SOL?
The link below says it can be done, but given my experiences in trying to remove my daughter’s fingernail polish from a carpet I’m a bit skeptical.
The solvent in all polishes that I’m aware of is acetone. You should be able to buy a pint at the local big box store. Armed with same and towels/rags that you are willing to throw away, you may be able to soak/blot the offending spot from the carpet, but I’m not really hopeful for ya. 
Should you decide to try it, bear in mind that acetone is highly flammable, and the rags/towels and the spot you’ve been working on will liberate flammable vapors for quite a while. Don’t smoke, extinguish pilot lights on stoves, and open the windows, or a spot on the carpet will be the least of your troubles.
Plan B depends on whether or not the carpet extends into a closet. If so, a carpet mechanic can sometimes cut out the soiled spot and replace it with a piece snitched from an unseen area. Good luck.
I’m a retired janitor, and I was trained in carpet cleaning. I disagree with the “flood with water” step in the link astro provided. First, it will spread the stain; second, the pad underneath might go moldy before it can dry.
Here’s my advice. Normally, I’d use a chloroethylene based spot remover, but for polish, I’d use nail polish remover. Open all the windows in the room, and start a fan. Get a pile of white rags or towels. Not colored, because the solvent may dissolve the dye, and it will bleed into the carpet.
Now, pour a little of the solvent onto the spot. You can work at the stain with the edge of a spoon or a coin, but don’t use a brush or a sponge. Making a small red spot into a big pink spot is not success. Put a white rag on the spot and stomp. Move the rag to a clean part, and stomp the spot again, drawing out the dissolved polish. Pour a little more, agitate, stomp again. Repeat until the stain is gone. It gets boring, but keep at it.
Warnings!
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Regular spot remover gives off nasty fumes, and polish remover is worse yet. Ventilation is crucial. If you start to feel woozy, leave the room immediately.
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These solvents will not only irritate your skin, but they can actually soak in and enter your bloodstream. Wear vinyl, or, better, nitrile gloves for this job.
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Nail polish remover is volatile and flammable. No flames or smoking in the same room.
Aaaaaand, if the spot proves to be stronger than you, a simple patch may be the answer. If you have scraps of the same carpet, cut out the stain with a razor knife. Cut a duplicate patch, and glue it in. Massage the edges with a comb to help hide the seams. Clip any stray threads with scissors.
If you are going to try nail polish remover, I would be sure to buy the non-acetone kind. The regular kind can actually melt some types of carpet. Yuck
Great idea Asknot.
Nail polish remover. Duh.
And yes blotting is the way to go. As a family that has had there share of dogs and cats, we know about that.
I’ll forward the ideas on this thread to my bro (he isn’t a doper [but his roomate that he just kicked out was, in the bad kind of way]}
Thanks all.
enipla.
Non-acetone polish remover doesn’t work very well, but it’s far, far gentler on nails, and of course is less likely to melt the carpet. If you’re gonna go with polish remover, you probably don’t want to get the kind that claims to have moisturizers and such in it.
Personally, I’d get some straight acetone, as it’s pretty cheap, and test it on a very small inconspicuous piece of the carpet, to see if it makes the carpet melt. If it does, then you’ll have to go with the non-acetone stuff.
One thing about dark red nail polishes…when I use them on my nails without applying a base coat of clear polish, I find that the color dyes my fingernails. Even after I use nail polish remover, my fingernails will still have an orangish-yellow stain on them that has to wear off. You might find that you can’t get all of the color out of the carpet, I’m afraid.