The basic rule in choosing an eye shadow is to go for a shade that contrasts with the eye color rather than one that matches it. For instance, it is best for those with blue eyes to avoid shadows in blue-green shades, choosing instead brown shadows with orange undertones.
To know which colors complement each other, become familiar with the color wheel. The colors opposite to each other are complementary. An eye shadow color that is opposite to the iris color provides contrast and makes the eye color more noticeable. It is also generally a mistake to try to match the color of the eye shadow exactly to the color of the clothing though it can be in the same family.