Before the advent of color instruments, color was evaluated by visually comparing the sample against the target color in a light booth that provided a neutral color background and controlled lighting. While the eye is still always the final judge, color professionals make use of the reflectance spectrophotometer to compare the L*, a* and b* readings of the sample and target and to provide a color difference. These readings are combined to produce a total color difference of DE*. In most instances, a DE* color difference of less than one unit is considered acceptable.

Once a color formulation goes into production, the sample initially approved by the customer is usually designated the production standard. Figure 10 shows the spectro’s readout for a recent production run of a formulated color versus the standard.