We investigate the intrinsic color characteristics used in accomplishing color constancy. The surface reflectance of an object can be divided into two parts: interface reflectance and body reflectance. The body component is the physical basis for determining the surface color characteristics of objects, but it is influenced by geometrical factors in measurement. To eliminate the effect of illumination and geometrical factors we adopt the normalized deviation reflectance, which was suggested by Tominaga, to describe the body reflection characteristics. Then, according to a finite-dimensional linear model, the body reflection characteristics are expressed in terms of weighting coefficients of the constrained basis functions, so as to reduce its dimensionality and make it easy to use in color classification. We choose objects made of inhomogeneous dielectric material as samples and use a grating spectrometer to measure their surface spectral reflectance, from which the description of intrinsic color characteristics can be derived based on normalized deviation reflectance and a finite-dimensional linear model. The experimental results show that this description is very stable under different conditions and also compact, so that it can serve well for color classification.