Quantitative models are used to predict printer output colors from a set of toner control values. The so-called Neugebauer model predicts the spectral reflectance of the printed colors. We present an algorithm for estimating the parameters of the Neugebauer model from a set of measured reflectances. The algorithm requires a bound on the magnitude of the output reflectance errors. A case study using a high-end color printer suggests that this algorithm yields robust spectral models, which are less sensitive (to undesirable variations in the data) than the models obtained with the methods of least-squares and total least-squares.