Multiple stripes of different colors of crackle polish with the top layer being a full coat of black crackle. The same effect could be achieved by using regular polishes to do stripes on the nail then topping off with the black crackle.
First a sponge gradient using China Glaze Go Go Pink and OPI Big Hair…Big Nails over Wet n Wild French White Creme. Then I stippled over that with China Glaze High Hopes. Unfortunately the gradient underneath doesn’t come out too much in the picture.