The image of jellybeans has vibrant and bright tones that can be difficult to accurately reproduce.
The 4-color printing process has limitations to what colors can be represented in their truest form. Many of the colors are close to fluorescent in hue and to reproduce them takes skill from the graphic designer and printer both. Colors can become flat if not correctly color managed, and they could become “dirty” if the press operator does not have control over the inks.
The varnish used is a technique that allows the designer to have a part of the image stand out, which can also help bring vibrancy to printed colors.
*Varnish is only visible on the printed target.