Artists typically employ two-dimensional color diagrams and three-dimensional color solids to organize the three variables of color: hue, value, and intensity. Artists' color models typically assign each color a specific point-location within the coordinate system of the color-space. Yet, artists have understood for over a century the phenomenon of simultaneous color contrast, whereby a given color will change its appearance in response to its color context. The variable identity of a color due to simultaneous color contrast is at odds with the invariant point- locations of traditional artists' color models. The author proposes a “territorial” model of color in which a single color may occupy one of many possible points in color-space, while at the same time retaining the overall hue-value-intensity organization of traditional color solids. This territorial model of simultaneous color contrast offers artists a representation of colors that more closely matches the dynamic nature of color perception, and it provides artists with some predictive power in creating simultaneous color contrast illusions.