How to find the right undertone for your foundation

The easiest way is to check your veins on your wrist in natural light - blue or purple veins usually mean cool undertones, green means warm, and a mix suggests neutral. You can also look at how jewelry looks on you; if silver flatters your skin more than gold, you're probably cool-toned, and vice versa. When you're actually at the store, swatch a few shades on your jawline or inner arm and step outside to see how they blend with your neck in daylight, since that's what matters most. Don't just rely on what looks good under fluorescent lights in the shop.