First of all there are two major types of colored contacts - enhancement color lenses and opaque lenses. Enhancement lenses are suitable for people with light eyes only, and are designed to make your own color brighter or give it a slightly different hue. For example: a person with naturally green eyes can wear blue enhancement color lenses and get most beautiful aqua effect.
You want your eye color to get brighter, but you don’t want to startle everybody who knows you with a different color
In this case, if you have light blue eyes, choose blue or aqua enhancement color contacts. You can also try Freshlook Radiance in Eden or Moonlight, which gives your eye an 'illuminated' effect.
If your natural color is gray or blue-gray, try blue from Acuvue 2 Colors or Freshlook Dimensions, to get a beautiful ocean blue color. If you feel more adventurous, go for jade green. Green eyes are quite rare, so you can make a statement with your new color.
If your eyes are brown, none of the enhancement color contacts would work for you. Try brown opaque lenses, which will make your color more defined, or hazel, which would make them lighter. You can also consider Freshlook Radiance Sunrise (lighter) or Autumn (darker), to add shimmer to your eyes.