Open the Corvette file or any colored image
Use the Quick Mask Tool at the bottom of the toolbar to select just the automobile. Use a hard, round paintbrush to “paint” over the car. Red represents the mask that you are applying. I used a 40 px, 100% brush. You may need to adjust the brush size to make more refined selections. Using the left and right bracket keys allows you to change the brush size quickly without addition additional mouse clicks.
Return to the regular editing mode by clicking on the Quick Mask icon again. The red will disappear and be replaced with marching ants. The area that you painted is not selected.
Add a new Adjustment Layer for Hue/Saturation to the image by selecting the icon at the bottom of the layers panel or by Going to Layer>New Adjustment Layer>Hue/Saturation. A mask will appear showing the car shape that you painted before. Remember white reveals, black conceals. The car will be hidden from this adjustment. Lower the saturation to -100. This removes the color of everything in the background.
To clean up areas of the image that need adjusting you can paint with white/black on the mask to reveal or conceal parts of the image.
TIP: A quick way to get the default white/black colors to activate is by pressing the D key on the keyboard. Pressing X will toggle between white and black allowing you to make quick adjustments without using additional mouse clicks.
Save your finished work.