For hard copy technologies using separate multiple layers of colorants to form the final output, differential gloss is a quality attribute that the ink formulator or toner process engineer must manage. In 2001, the standards committee from INCITS W1.1 issued in 2001 40-patch multicolor test target for the evaluation of differential gloss. The use of this target typically involves reporting the maximum and minimum gloss readings among the 40 color patches. This paper proposes a methodology to interpret the extent of differential gloss in terms of just noticeable differences, or JNDs, and to diagnose how gloss level changes with color or lightness levels. Examples of several electrophotographic and inkjet outputs will be used to illustrate the standard target and the methodology.