Back in the day and even to some extent today, artists and photographers would take a black and white photo and hand color it to add richness or a more life-like presentation. I always enjoyed the look of a fine hand colored black and white image. My favorites were the ones where the artist added just a splash of color to the image. Sometimes you would see an abstract colorization attempt that pulled it off as well.
In our modern digital age we can effectively do the same thing. We can take an image and convert it to monochromatic shades of gray and then add color as we see fit. This can be a tedious task just as hand coloring was for some of us. Although if minimal color in a specific area is the goal this is an easy method using a simple mask and paint brush. The photo of the woman with only the green eyes is an example. The football picture was done in a pixel editor like Photoshop or Corel and used a specific mask to separate the one player from the rest. There is another way to have some fun with hand coloring but it is simple and kind of in reverse.
Using Adobe Lightroom you can take a full color image and begin removing all the color saturation from specific colors. By moving the sliders to remove color and leaving others a similar albeit less precise effect can be had in a fraction of the time. Lightroom is very limited on masking so this may create an abstract image. Sometimes it works and sometimes it doesn’t. When it does it can be a really amazing take on an otherwise morose scene.
This desaturation technique can be most effective at changing the mood of a photo. Black and white can often conjure up a gloominess that color would struggle to capture. The limited and creative use of color in the scene can keep the somber feel while providing a splash of color. Play a round with your images and have fun creating something very different from what your camera produced.