They look cool and can really help sell an image. Whether you achieve the end result in Photoshop, Photoshop Elements or on your smart phone – don’t over do/use it. Remember to be selective with your image choices and again – this needs repeating – do not over do it. If you’re shooting a model portfolio or wedding it’s nice to maybe have one spot colour image, but that’s about it and only if there is a image that is enhanced by the process.
There are tons of free tutorials on line that will explain how to achieve this look. There are many different methods that can lead you to the same result. Find what works for you by trying them all. After doing several you’ll start to see what works and what doesn’t. Some images you’ll have the item or object you want to stand out as the spot colour, which is typically the norm with this effect, but you may also wish to try inverting the mask and having the dominant item as shot in B&W with the rest of the image as a colour.