Why does a white skin turn yellow while putting pressure on it?

When pressure is applied to the skin, the blood vessels near the surface contract, restricting blood flow. This decreased blood flow causes the skin to appear pale or white. As the pressure is released, the blood vessels re-expand and blood flow returns, causing the skin to return to its normal color.

In some cases, the skin may appear yellow rather than white when pressure is applied. This is because the pressure can also cause the release of bilirubin, a yellow pigment that is normally transported by the blood. When bilirubin is released into the skin, it can cause the skin to appear yellow. The yellowing of the skin will usually disappear once the pressure is released and blood flow returns to normal.