For this photo, I created a mask of the baby to keep its color, then added the black and white on the background. I then adjusted the brightness and contrast to deepen the shadows. 

On this photo, I added a hue/saturation layer. I then selected the baby and inverted her colors and added a purple hue. Then I adjusted each hue to enhance the shadows and highlights. 

For this photo, I played around with the brightness and saturation, then added a orange and purle color layer on top. I also selected the swing seats and the purple bars at the top to enhance thier color as well. 

For this photo, I added a color layer to put a faint color across the whole picture. Then I selected the baby to make sure she stayed the same color. Then I pressed invert and the colors changed to purple and deep pink. 

On this photo, I created a mask of the baby to keep its color, then added the black and white on the background. I then adjusted the brightness and contrast to deepen the shadows.