It’s a very simple idea: just keep one object or person in your black and white shot in color and that object will catch everyone’s attention. As you can see in the following pictures, the result is captivating.
Montmartre by John Althouse Cohen
Have a Heart Desaturated Free by D. Sharon Pruitt
Highway Insomnia by Brett Weinstein
Blue Eye by Rob
Piedras de primavera, spring stones. by Vicente Villamón
driving musicians by Till Krech
Beauty & the Beach by Dr. Wendy Longo
Source: www.photographyblogger.net/20-black-white-pictures-with-a-bit-of-color/