The Color Wheel is your Friend

Back to middle/high school physics lesson. Between the hiding your gum and doodling your crush's name onto the desk then immediately erasing it, you probably learned that light is made of 3 primary colors - green, blue, and red. The complementary colors (combining 2 of the primaries) and their opposing primaries create white, the most vibrant color. Green and blue create cyan, which is the complementary of red. Blue + Red = Magenta, and Magenta + Green is white. Red and green create yellow, which is the complementary is blue. And believe it or no, we can apply it to makeup!

Complementary colors really make eyes "pop," and they sit opposite each other on the color wheel.

For example, darker blue eyes are really brought out by yellows and golds. Lighter ("cyan") can be amplified with red lipstick. 

Green eyes are exaggerated by pinks, especially bright magentas.

Brown eyes are strengthened by blues!

(All of these pictures are courtesy of Makeup Geek)