Dell S2740L User Manual page 34

Input Color Format Allows you to set the video input mode to:
RGB: Select this option if your monitor is connected to a computer or DVD player using the VGA and DVI cable.
YPbPr: Select this option if your monitor is connected to a DVD player by YPbPr to VGA, or YPbPr to DVI cable; or if the DVD color output setting is not RGB.