Birefringence and Cygnus Loop look very similar in the bottle. Birefringence is more blue/purple with more multi colors at different angles. Cygnus loop is more purple/pink and even though the colors shift at certain angles, I still think there's more color shifting with Birefringence. They are both really stunning polishes. I only needed two coats and 1 topcoat of Seche Vite.
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