For a student of architecture in 1958, the Munsell system was a revelation. Munsell's hue, value, and chroma were perfectly clear, but then they were challenged by the Ostwald system with its white content and black content. The revelation was followed by confusion. It became evident that there is no such thing as a single correct colour solid or, indeed, a single correct colour circle. Colour circles can be structured with equally spaced primaries or organized so that complementary colours are opposite to each other, but different systems have different sets of primaries, and the different ways of establishing complementary relationships yield different pairings. These different relationships can be reconciled if the circle is treated as elastic with intervals between colours stretched or compressed to show the relationships relevant for a given situation. In the third dimension of a colour solid, the principle of elasticity can also be applied to show relationships of value, of whiteness and blackness, and other dimensions as they are variously defined. The structure of Munsell can be morphed into that of Ostwald and other systems where colours are ordered according to different principles. If the colour solid is regarded as elastic, it is easier to understand the information embodied in the structures of different colour order systems and also to see how they relate.