This article addresses the problem of colour constancy: how a visual system is able to ensure that the colours it perceives remain stable, regardless of the prevailing scene illuminant. My aim is first to summarize and review the most important theoretical advances that have been made in this field. Second, I present a comparative analysis of algorithm performance that we use as the basis of a discussion a the current state of colour constancy research and of the important issues that future research in this field should address. Finally, I highlight some areas of recent research that are important in the context of further improving the performance of colour constancy algorithms. (C) 2006 Wiley Periodicals, Inc.