When you're ready for red lips, you need to consider skin tone. This seems like it would be easy, but I actually had a hard time deciding into which category my skin falls. Most makeup experts classify skin as light, medium, olive, dark, or deep. For those who fall in between, I recommend using Bare Minerals' Shade Finder and Becca Cosmetics' Skin Tone Finder to determine your tone.

Warm, cool, and neutral are the terms generally used to describe the undertone or tint of skin. There are a few ways to figure out your undertone.

-The Vein Test: Flip your wrist over. If you've got bluish-purple veins, you're cool. If your veins are green-ish, you're warm. If you're having difficulty deciding if they're blue or green, you're probably neutral.

-The Jewelry Test: Hold a piece of silver jewelry and a piece of gold jewelry against your skin in natural light. If you look better in silver, you're cool. If you look better in gold, you're warm.

-The Color Test: Your hair and eye color can help determine your skin tone. Think back to when you were a child. Did your hair have hues of orange, yellow, red or gold? Are your eyes amber, dark brown, hazel, or green? If you answered yes, you have warm skin that is usually golden or apricot. If your hair had tones of blue, violet, silver, or ash and your eyes are light blue, gray-green, blue-green, turquoise, gray, black, or cool-brown, you have cool skin with a pink or rosy undertone.

"Most lighter-toned skins look best in true blue-based reds," says celebrity makeup artist Amanda Shackleton. Allie's cool, fair skin was the perfect tone to test the theory.

Allie Loved: Like Shackleton suggested, Allie tried to find a true blue-red, but ended up liking this warm red best. Cle de Peau Beaute Extra Rich Lipstick, $60, in Warm Abundance felt "classic red" to her. "This lipstick was long-lasting and felt versatile -- I can wear it during the day or at night."

Not So Much: Avon Ultra Color Lipstick in Cherry Jubilee, $8, was "way too dark" for Allie's preferences. "I like the formula of this lipstick, but I could never wear this during the day. Maybe if I figured out the right makeup to wear with it, I'd wear it at night."

If you have golden tones in your hair, celebrity makeup artist Scott Barnes recommends "going a little more coral-red to bring warmth to your coloring." But, be warned: "Do NOT go orange, ever," Barnes adds. Orange lipstick, while trendy and eye-catching, makes your teeth look yellow.

Emily Loved: Merle Norman Age Defying+ Lipcolor in Americana, $15. "I LOVE this blue-red. It's the shade I think of when I think of a true red lipstick. This shade feels classic and iconic, and the blue of the lipstick makes my teeth look white!"

Not So Much: "I tried a coral red, (Elizabeth Arden Ceramide Ultra in Flame, $22.50) but I just couldn't get over the orangey-ness of it. It felt comfortable, because it's less 'look at me,' but it wasn't the red I'm looking for."

For cool-toned brunettes (think: Lily Collins), Barnes recommends a soft red. "You'll end up looking like Cruella De Vil if you go to bold," he warns. "Nars has some great sheer reds."

Hayley Loved: NP Set Lipstick in Gold Coast, $22. This deep red is pink-based, which works with Hayley's skin tone. "I like true reds with pinkish undertones, so this is my go-to red lipstick."

Not So Much: Hayley was not a fan of Maybelline's Color Sensational Vivids Lipcolor in Neon Red, $5.49. "I don't know how to pair the rest of my makeup with it because it's so bright -- I don't want to do dramatic eyes, because that seems like too much, but I also don't want to go without eye makeup. It's too bright for fall, but too high-maintenance for summer."