what do you call this color effect that is almost black and white except for...

[-ayen sugar_cane]

...one color existing in a photo? guys, what do you call that color effect wherein the photo is almost black and white except for one thing that has color in it?

 

[Stephanie Ann]

It's usually called "Selective Coloring." But is also often referred to as "Spot Color."

It's an amazing effect to work with, and quite fun!