A method to statistically process real input and output data from a color input or output device and predict the color-transfer characteristics from an arbitrary input or output signal, or from the output signal and a part of the input signal to predict the remaining part of the input signal. Real input and output data pairs and prediction-source values are prepared which are used to calculate initial values for weighted coefficients. Matrix elements and the prediction value are calculated so that the sum of the squares of a distance between the predicted output and the corresponding plurality of real output data, weighted with a weighting coefficient, is minimized. The matrix elements and the prediction value are used to recalculate the weighting coefficients.