Why you need it: Pastels may make you think of spring, but they're beautiful against winter whites and sun-tanned summer skin, too. Pastel nail polish gives any manicure a ladylike, clean look, and they're a beautiful base for nail art.

When to wear it: When you're tired of pale pink or nude; for Pinterest-worthy nail art. (Ombré! Polka dots! Stripes!)

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JinSOON, Aero, $18. Picture this hip sky blue against light-colored denim -- gorgeous, right?

China Glaze, Partridge in a Palm Tree, $7. Milky mint is a pastel hue that always looks fresh.

Floss Gloss Nail Polish, Palazzo Pleasures, $8. This dusty lavender is the darker side of pastel, with just enough gray to look hip and modern.

Why you need it: Gemstone-inspired polishes look rich and sophisticated. They also have the benefit of being almost universally flattering, capable of brightening almost any complexion. Who doesn't shine in shades like emerald, turquoise or pink tourmaline?

When to wear it: With special-occasion outfits, especially in the cooler months and for evening events.

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Dolce & Gabbana Beauty Intense Nail Lacquer, Wild Green 725, $27.50. This new, emerald greene crème would look gorgeous on a cool blonde or redhead -- and green polish is so hot right now.

Yves Saint Laurent La Lacque Couture, No. 77 Vintage Plum, $28. Amethyst polish -- like this new one from YSL -- is a super-feminine alternative to pink and red.

Essie Nail Color, Starry Starry Night, $8.50. For a limited time, Essie has revived this microglitter-flecked, sapphire blue polish, originally released in 1985. Get it while you can.

Why you need it: Glitter polish isn't for everyone, but metallic shades are festive and fun without appearing over-the-top. Precious metals like silver, yellow gold, rose gold and bronze are classic nail colors; shades like black rhodium and green gold are beautifully unexpected.

When to wear it: Metallics feel right for parties, holidays and fancy dinners -- any celebratory occasion -- but a pretty metallic is just as versatile as any neutral.

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