If I sit directly in front of my new 20 inch Imac the colors in a picture look great, but when I move my head ten inches left or right, up or down, the colors change quite noticeably, either lighter or darker. I've looked at other twenty inch Imacs and they've all had this problem. The twenty four inch Imac has somehow avoided this problem as there is no loss of color while viewing from any angle. What would cause this, and more importantly can anything be done?