I love red nail polish, even though it's probably the worst possible color choice for a paper crafter. I try and limit it to my toes, but every once in a while I just have to do my fingernails.
And inevitably something like this will happen—a red mark left on my paper from the polish. However, I have figured out a way to remove that mark—sometimes—it's not fool proof. Mind you, it won't work on a patterned paper nor will it work directly on a colored image (it takes off a bit of the top paper layer) and it doesn't work as well on glossy papers, but on lighter colored papers or in a lighter colored area, it can work. If it means keeping your project or throwing it away to start all over, it's worth a try. Here's how:
1) You have a red mark on your paper left by an inadvertent swipe of your hand (grrrrrrrrrr....).
2) Take a white "magic" sponge and gently mist one corner of it with water. You don't want to saturate it; you want it just a tiny bit damp.
3) Rub the tip of the sponge gently on the red mark. You'll see that it's taking away a bit of the paper's top layer. Don't rub too hard.
4) Voila! The red mark is gone (do let the paper dry before proceeding). Again, not a perfect method by any means, but in a pinch it's worth a try.