The official term for the red thing on a turkey is a wattle. The wattle changes color as the turkey gets excited or angry.
The wattle also changes color when the turkey is looking to mate. Normally light red or dark pink in color, the wattle changes to bright red during these occasions. The wattle hangs from the turkey's chin and it resembles a loose flap of skin.
Turkeys also have a snood. The snood is a red piece of skin that hangs across the bird's beak. This can also change colors if the turkey is upset or looking to find a suitable mate.