Grayscale color mode, also known as black and white color mode, is composed of two colors: black and white. It is used to reproduce an image with different shades of grey.
A computer monitor represents only one form of black. In print, there are several ways to represent black, including “rich black.” Rich black is a darker, deeper black that combines a percentage of all the four CMYK inks. The values to create rich black for coated stocks are: C = 30, M = 30, Y = 30, and K = 100. The values to create rich black for uncoated stocks are: C = 20, M = 20, Y = 20, and K = 100. For gray densities, we recommend that the file have the following color values: C=10, M=10, Y=10. For the K value, anything under 100 would be considered a gray.