Environmental laws mandate the protection of visibility conditions in national parks, and wilderness areas from atmospheric haze due to the emissions of anthropogenic air pollutants. To calculate the improvement in visibility that results from the reduction of these air pollutants, it is necessary to quantify the relationship of haze to the color appearance of objects being viewed through it. To this end, a field study was conducted in the Great Smoky Mountains National Park in eastern Tennessee. Color appearance of objects was quantified by color matching with a visual colorimeter. The Hunt94 color appearance model proved to be an invaluable tool that allowed color appearance of natural targets determined by an observer with a visual colorimeter to be compared to the color appearance predicted from the observed spectra of the target. The variable outside adapting conditions were quantified in terms of the model parameters by finding the values of the parameters that gave the best agreement between observer and spectrophotometer for a set of standard color cards. These model parameters were then applied to the natural targets. In this way, the differences between the adapting and observing conditions of the visual colorimeter and the natural outside environment could be reconciled. The apparent hue, colorfulness, and lightness of objects seen at a distance through haze are strongly dependent on perceived transparency of the atmosphere. The hue is approximately constant with changes in the optical depth of the haze. Lightness behaves similarly to hue. Colorfulness decreases exponentially with optical depth.