We studied the individual variability of asymmetric metameric colour matching between computer displays and object colour stimuli in conditions typical for the surface colour industries. Using two different computational techniques. we assessed the contribution of observer metamerism to this variability. It? the studied conditions of spatially separated computer display and surface colour stimuli, this contribution was found to be insignificant for all colours but neutrals. In the chromaticness plane, the range of matches made by different observers practically coincides with the range of matches made by at? individual observer. Consequently, we conclude that it? the task of matching spatially separated display and surface colours, the range of matches made by a group of observers cannot be determined from variations it? their colour-matching funtions, and thus the paradigm of the Standard Deviate Observer is shown to be inapplicable to the studied conditions. We suggest that individual variability in these conditions is governed by mechanisms of chromatic discrimination, and can be modeled by advanced colour difference formulae with suitably adjusted parametric coefficients. (C) 2008 Wiley Periodicals, Inc.