On a computer screen there is only one way to represent black. In print, there are many different tones of black and all are determined by the CMYK build. A build of 100% K alone will result in a dark gray. Rich black is defined as 100% K with the addition of Cyan, Magenta and Yellow to darken the final print of a solid black. C-70%, M-40%, Y-20%, K-100% are the suggested RGB values to obtain the darkest black in printing.