In this paper, the decoding model of color vision is briefly introduced. The θ-r-z color system, which is based on the decoding model and has both the features of the Munsell color system and those of the XYZ system, is proposed. The θ*-r*c-z* color system obtained from nolinear transformation of B, G, R, is provided. The decoding model is verified by both the reflection of e and z* to lightness and the distribution of the color samples of the Munsell system in θ*-rc*-z* system.