Delta E measures the difference  between colors

⬥Printing restricts color and is imperfect

⬥“That’s not Pink, it’s purple”

⬥Measuring helps to set expectations for variance in color

Printing has a number of variables that can shift the expected color results from Design thru Production. It's not uncommon for personal viewpoints to describe the same color differently. This can be caused by known issues such as lighting conditions or limitations in the eye. By using a measurement method to evaluate color, you can best determine where the change in color is taking effect. Delta E provides that measurement to compare spot color to spot color.