To characterize color values measured by color devices (e.g. scanners, color copiers and color cameras) in a device–independent fashion these values must be transformed to colorimetric tristimulus values. Often it is assumed that RGBs are approximately linearly related to XYZs
and so this transformation is determined by least–squares (LS) linear regression. While the LS method is guaranteed to minimize the residual squared error it makes no a priori statement about which colors will be mapped well and which will be mapped poorly. However, we argue that such
a statement must be made. In particular because it is important to preserve the white and the gray-scale in color reproduction, we argue that achromatic colors should be preserved in color correction. This argument led us to develop a new regression procedure: the
Graham D. Finlayson, Mark S. Drew, "White-point preserving color correction" in Proc. IS&T 5th Color and Imaging Conf., 1997, pp 258 - 261, https://doi.org/10.2352/CIC.1997.5.1.art00051