So, this technique gets overused a lot. I especially can't stand when someone actually uses it to take attention away from the subject. Like a picture of a kid, where some random color on his shirt is highlighted.
Here I used it because I liked the framing in this picture, but Brice's color is more or less the same as the color of the background, making him not stand out as much. So, I put the background and the foreground in black and white, but left him colored. I'd rather have him against a nice, natural contrasting background, but with what I had to work with, I think this really saved the picture.