Color fringing in photos is most often due to chromatic aberration, when a camera lens doesn't focus all colors onto the same point. It's a common problem, especially with cheaper lenses, but we may soon be seeing much less of it thanks to a new breakthrough at Harvard.
The Canon 35mm f/1.4L II lens announced back in August 2015 was the first Canon lens to feature the company's new Blue Spectrum Refractive (BR) lens technology, a special lens element that corrects for color fringing.
Photoshop and Lightroom both have built-in tools for dealing with chromatic aberration (AKA color fringing), but in some cases the features don't work as well as you'd hope. In the 8-minute video tutorial above, photographer Steve Perry of Backcountry Gallery shares a quick and easy trick he uses in Photoshop to manually remove fringing from his shots.