These remind me of gobstopper candies I used to eat when I was a kid. I was constantly pulling them out of my mouth to see what new colours I had revealed by sucking on them. haha
To make these nails you simply put single coats of various colour polishes and then use a brush dipped in nail polish remover to wash away the layers underneath.
The nail polish colours involved with this were Avon's Pastel Pink, Lagoon, Sally Hansen's Mellow Yellow, followed by Avon's Sweet Mint and finally Luxe Lavender. It is almost impossible to see the yellow as it blended in with the green too much.