VGA Signal Generation with the XS Board This memo discusses the timing for the signals that drive a VGA monitor and describes a circuit that will let you drive a monitor with the XS Board . VGA Color Signals There are three signals -- red, green, and blue -- that send color information to a VGA monitor .   These three signals each drive an electron gun that emits electrons which paint one primary color at a point on the monitor screen . Analog levels between 0 (completely dark) and 0 . 7 V (maximum brightness) on these control lines tell the monitor what intensities of these three primary colors to combine to make the color of a dot (or pixel ) on the monitor’s screen . Each analog color input can be set to one of four levels by two digital outputs using a simple two - bit digital - to - analog converter (see Figure 1) .   The four possible levels on each analog input are combined by the monitor to create a pixel with one of 4 ´ 4 ´ 4 = 64 different colors .   So the six digital control lines let us select from a palette of 64 colors . Figure 1: Digital - to - analog VGA monitor interface .