An image that looks great on a video monitor, for example, may look very differently as a color print. In other instances, we may wish to fine tune the colors of the image to reduce unwanted effects. These are fine for display on video monitors, but are not suitable for color printing.
Professionals employ the CMYK color model for producing color separation plates for printing.
Black is added for details and the remaining are the subtractive primaries or pigments that you probably used in grade school to mix colors. Our task is to convert the RGB image into a CMYK image. At the same time, we should correct its color so that it prints reliably and looks more natural in the printed medium. Suppose that we decide that the morn1.jpg image has too much yellow in it. We can correct this by reducing some amount of yellow in the entire image.