This is one of the most noticeable picture problems when it is not set correctly. To begin with, turn the setting all the way up and down so you can have a better idea of what is changing in your image. When the color is set all the way to zero, the image becomes black and white. When set at the maximum, the picture becomes red.
For this calibration, use a scene with flesh tones. The scene I used in "Life is Beautiful" featured relative close-ups of two people, with green plants behind them. Focus on the faces of your selection and watch for subtle changes towards red or towards a more washed out color. Play in that range until you find the most natural looking flesh tones. Keep an eye on other signals like plants or flowers in the background. All elements should remain looking very life-like.