Lightroom - Remove Chromatic Aberrations

Chromatic aberrations are a form of optical distortion caused by a failure of the lens to focus all of the colors to the same point. It is most noticeable at the contrast transitions, e.g. between a building in the foreground and a bright background. It generally looks like either purple or green fringes of color around objects.

Lightroom is able to hunt down and take care of the problem at the touch of a button. Just head into the Lens Corrections panel, and check the radio button for Remove Chromatic Aberrations.