Variability in object appearance is common in everyday experience and this variability can generally be attributed to the relationships between viewing conditions and the composition of an object's spectral reflectances. This paper proposes that objects, illuminants, and observers can be evaluated using a Wpt (Waypoint) shift manifold (WSM), which is defined as a set of Wpt points associated with one or more objects, observers, and/or illuminants. Since spectral reflectances of an object can be decomposed to three components (a wavelength invariant nonselective component, a characteristic reflectance, and a metameric black reflectance), WSMs of any object for an observing condition is composed of three Wpt vectors associated with a perfect reflecting diffuser, the characteristic reflectance, and the metameric black reflectance of the object. Material shift potential (MSP) can be defined as shapes and orientations of object WSMs for evaluation and comparison of object colors. Experimental results show that MSP are dramatically influenced by Wpt vectors associated with the characteristic reflectance and the metameric black reflectance for an object rather than the Wpt vectors associated with nonselective reflectance. Thus, MSP can be preserved for objects having similar characteristic reflectances and metameric black reflectances. In other words, spectral reflectances that have been manipulated to have similar overall shapes exhibit similar color inconstancy.