This article examines the role of colour as an integral consideration of material selection. It suggests that an understanding of colour, and its potential to alter the general perception of form, space and surface, is as essential as any other material property. Recent developments have led to a period of growth in the use of colour in architectural design, for example through highly pigmented ceramic tiles, back-painted glass facades and pigmented concrete. These offer permanent and durable surfaces. The potential of colour to alter the perception of space and form brings with it a certain anxiety in its use, particularly when embedded on the exterior surfaces of buildings. Yet decisions on colour are often arbitrary and left until late in the design process. The article will consider colour and material surface, colour as conceptual material, the elusive properties of colour, which are entirely contingent on light conditions and context, and colour specification in the design process.