While anyone can look gorgeous wearing eyeshadows that span all the colors of the rainbow, there are certain shades that are a sure bet on certain eye colors. It's all about color theory — that thing you learned about in your middle school art class. If two colors are opposite one another on the color wheel, they tend to compliment one another. That theory works in makeup, too, which makes shopping for the best eyeshadow palettes for brown eyes pretty simple when you know what undertones to look out for. In other words, it's time for an art lesson.
Brown is a neutral, so most colors will pair well with it. But to really make them dazzle, you want to look for colors that lie on the other side of the color wheel. Brown is formed by combining either two secondary colors, or a primary and a secondary color — typically, using a combination of red, orange, and/or yellow.
If you're dealing with a brown that has more orange or yellow undertones, you'll want to go with purple shade, since it falls opposite on the color wheel. Similarly, if your brown eyes have more red tones, green will really make them pop. Also, a grey or silver smokey eye will look stunning, because the coolness of those tones works beautifully against the warmth of brown eyes.