Chromatic aberration is the failure of a lens to focus all colors to the same point. To a cinematographer this can be an undesired effect, but in motion graphics it can be a very nice addition. While it would be great to capture chromatic aberration naturally with real lenses, most modern lenses aim to minimize this effect. This is why we are dedicating this tutorial to learning how to recreate this phenomenon using built-in after effects plugins.
LINK:
http://ae.tutsplus.com/tutorials/motion-graphics/learn-how-to-create-chromatic-aberration/