Hello again everypony!
It's another fabulous Rarity post! (for those of you wondering why I haven't gotten to Applejack or Fluttershy yet, don't worry, they are coming)
This manicure is quite easy, actually. Based on the classic French manicure, because you know anypony as fashionable as Rarity deserves nothing less.
Two colors are needed. White (I used one from Claire's, but I do recommend getting something better--I did this earlier today and already my nails are chipping!)
and a deep purple (NYC #205-Midnight Amethyst)
First, paint your nails with the white. You'll likely need two coats.
Then, paint the tip with the purple. To get that beautiful little half-moon shape, use small strokes instead of trying to do one line. It also helps to have your hand flat on a table.
And voila! You have Rarity nails.