rainbow effect 
A visual artifact that occurs in single-chip DLP displays, caused by the fact that the single DLP chip uses a color wheel to create red, green, and blue, and hence all colors. Occurs primarily when the eye looks across the screen or when adjacent areas of very dark and very light material move quickly. The occurrence of these rainbows has been significantly reduced with the advent of newer, faster color wheels, and most people who watch a DLP never see rainbows at all--and the few who do, usually see them only occasionally.