A spot color dictionary is fine tuned or updated. Localized color production models are determined for spot colors of interest to be produced by an associated document processing system or printer. Measurements are made of colors of produced spot colors. Optionally, measurements are made of colors of test patches that are based on perturbations from the colors of the spot colors. In determining a model for the production of a target spot color, measurement data related to colors that are closer in color space to a given target color is given a higher weight than is measurement data related to colors that are further in color space from the target color. Accordingly, the model is localized to the region of color space about the target color and therefore, more accurately predicts a colorant recipe for the target color than would interpolation based on a full gamut, or more general model.