A.M.
Hi there,
This happened to us recently as well. My girls got bright pink nail polish on our new, off white carpet. I know it's going to sound weird - but we used unscented baby wipes (Huggies brand) and it got the nail polish out. I swear by wipes to get almost anything out of carpet. I've used them before on pen, grease etc and they've always worked. You have to dab/rub at the stain over and over again (using multiple wipes) - but like I said, we've had success that way. My girls are 9 and 5 and I always keep wipes in the house for carpet stains!! Also, there is another product called "Goof Off" that may work to get nail polish out. It's very powerful and strong smelling. We only use it as a last resort and make sure to open lots of windows, turn on fans (to ventilate well) and we try not to use it with the kids in the house.
Good luck!
A.