This t-shirt color will tell you if you have warm or cool skin undertones

When you reach for your foundation or concealer, you’re actually making two color decisions: the first is (obviously) that you choose a shade that blends imperceptibly with your skin. The second is directly related to making that a reality: You’ve got to pick a shade in which the undertone of your formula matches the undertone of your skin.

The thing is, though, it’s not always easy to figure out, so I asked a pro makeup artist her trick for how to figure this out once and for all. “It’s really important to know your skin’s undertone,” Jane Iredale, founder of her eponymous brand and makeup guru, tells me at an intimate meeting in New York this morning.

There’s the vein trick (where you look at the vein in your wrist: green means warm, blue means cool), but there are other ways, too (because vein colors can be tricky, ya know?). Some say that if you wear gold jewelry, you have a warmer complexion, while if you favor silver, you might skew a bit cooler. But Iredale says that all you’ll need is a pink or a peach T-shirt. “The foolproof way is called draping, where you drape yourself with certain colors to see which flatters you,” says Iredale. “If you hold a pink up and look in the mirror, it’ll either look flattering or it’ll enhance your eye bags. Do the same with peach and vice versa. You’ll really see your complexion change.”

If the pink is more your hue, you’ve got cool undertones; while if the peach works better, then you’re on the warm side. So now you know what to look for when shopping for your makeup staples and of course, what your OOTD tomorrow will be.

Speaking of your makeup look, here’s Jennifer Aniston’s genius lipstick hack and Cindy Crawford’s secret to perfect eyebrows.