Just playing around with my nail polish collection this week as we are now only a couple of weeks away from Halloween, and I came across this cool combination that I think is Halloweeny but also pretty.
Start with 3 coats of Essie in Devil's Advocate (it's a really dark purple that looks almost black but is nicer since it has the violet undertone).
Add a coat of Revlon in 745 Pink Glaze (one of their "Transforming Effects").
Top with a clear top coat (I use Revlon Extra Life No Chip Top Coat).
Voila! Pretty and still a bit ghoulish. Hope you have a proper costume party to wear it to!