Wavelength information serves both to organise shapes and to provide the appearance of surfaces. These two roles are considered within a model that outlines the role of colour in picture naming (Davidoff and de Bleser, 1993). An introduction to the papers in this issue is given within the framework of the model. The topics in this issue cover the role of colour in scene segmentation, colour constancy and the memory for the colours of objects. (C) 1997 Elsevier Science B.V.