A B&W conversion experiment. Decided to use a bit of selective color to "point the way". Easy to do with Nik's Silver Efex Pro (SEP). After converting to B&W in SEP to your satisfaction -
Exit SEP by selecting the Brush option,
Use the brush's Fill option to convert the entire image to B&W,
Use the brush's Erase option to brush away the B&W where you want to return to the original color,
Done.