Here, we have a busy picture of myself. Let's say I want everyone else in the photograph to be black and white, with just me in color. It's possible!

Into:


Open up your image and go to your Tools. At the very bottom, there will be a button where you can enter Quick Mask Mode.


Double click on it to adjust your settings.


Now, use your Paint Brush tool and select a basic brush. Make sure your brush is at 100% hardness. Paint over the part of the image you want to remain colored. It will turn red, which means that it has been masked.


Exit Quick Mask Mode after you're done by hitting Q on your keyboard, or clicking on the button. The entire image will look selected. Go to Select >> Inverse on your Options bar. Now only what you masked should be selected.

Copy and paste this into a new layer. On the original layer, go to Image >> Adjustments >> Desaturate.