Chromatic aberration is the unwanted distortion of colours that you sometimes notice on the edges of your photos. It happens because colours of light have different wavelengths, which means your camera lens refracts them slightly differently. Here's a quick fix to compensate in Photoshop.
The effect is usually most pronounced around the outside edge of photos where hard lines make it clear where different colours don't quite align. In this video from Jimmy McIntyre, we learn an easy way to minimise the presence of chromatic aberration.
There's no precise adjustments for colour realignments in this method; rather, he simply duplicates the photo, uses gaussian blur with a radius of 20 pixels (which you should adjust depending on the size of your photo), and then sets the blurry layer's blend mode to 'colour.' This removes the aberration but smudges the colours of the entire photo, so the next step is to make a mask so you can control where you want the effect applied.
And that's it. As he says in the video, McIntyre also offers presets that you can download to make it even easier.
Quick Photoshop Secrets 4: Quickly Remove Chromatic Aberration [Jimmy McIntyre]