There are a number of capillaries close underneath the nail. When you press on the nail, it forces the blood out of the capillaries, and the nail appears lighter. When you release it, the blood flows back and the nail "pinks up." When I used to work as an EMT, that was an evaluation tool we were taught. When you press on someone's nail, it should pink up again in less than the time it takes to say capillary refill. Otherwise, there is a circulation problem.

Any part of your flesh does that. When you press your nail you're pressing the flesh underneath it. That pushes the blood out of that part temporarily.

When you press down on your nail or any other part of your body, the blood vessels are compressed and are forced away from the pressure.

They are not nails that turn pale - its the flesh under them that gets pale. The blood is squeezed away from the place you press it. Not right?

Because you're pushing the blood away.

Because you're pressing the blood away. :-)