Why you need it: Why do you need red polish and deep red, you ask? Oh, child... If a red polish is tried and true, appropriate for any occasion, then deep red is its slightly moodier, less predictable sister. You can't wear it with everything, but when you do wear it, you'll feel sexy, feminine and tough.

When to wear it: With a dressy or edgy outfit, especially in fall and winter.

Try...

Chanel Le Vernis Longwear Nail Colour, Vamp, $28. Burgundy bordering on black, this polish was a must-have in the mid-1990s, and was recently re-released due to popular demand.

NARS Nail Polish, Chinatown, $20. It's hard to imagine this cult-favorite oxblood enamel looking bad on anyone.

Julep Nail Color, Scorpio, $14. This bordeaux polish from Julep's new Zodiac Collection is sprinkled with a purple-y red shimmer for a look that's edgy and modern.

Why you need it: Sometimes, you want the attention off your nails -- but you don't want to go totally naked. Nude nail polish is the best color for an understated mani, and it makes raggedy nails look about a million times better. The right nude nail polish doesn't look like polish at all -- just beautiful, clean, shiny nails.

When to wear it: For conservative occasions, or to contrast a bold outfit or statement makeup.

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Oribe The Lacquer High Shine Nail Polish, The Nude, $32. Oribe recently launched an edited selection of eight-free nail polishes -- one red, one plum, and this lovely, warm beige.

Yves Saint Laurent La Lacque Couture, No. 22 Beige Leger, $28. This classic, pinkish nude looks pretty against pale, cool complexions.

Zoya Naked Manicure, Nude Perfector, $10. A genuinely nude nail color is different for everyone, but this beige polish is sheer, so it works with a variety of skin tones. It's also formulated with a variety of vitamins and minerals to restore nail health.

Why you need it: Greige polishes seemed like a passing fad in the late 2000s, but we're glad they stuck around. Neutral polishes like gray, beige, white and cream are more noticeable than pale pink or nude, but versatile enough to work with almost any outfit.

When to wear it: It's great for every day, as your go-to work-week polish, with bright clothing (to avoid clashing) or a neutral ensemble (for a chic monochrome look).

Try...