Colour patterns on mollusc shells are usually controlled by one-dimensional morphogenetic programmes. In adult cypraeids, by comparison, colour patterns are two-dimensional in morphogenesis and three-dimensional in structure. Visible patterns usually result from the uneven thickness of a pigmented layer, rather than from a spatially uneven concentration of pigment. Specialized sculptures in a few cypraeids may be regarded as extreme examples of three-dimensional colour patterns. Morphogenesis of some patterns is controlled by three-dimensional relief of the underlying shell surface. Computer models successfully reproduce key characteristics of cypraeid colour patterns. Since most cypraeids possess colour patterns, while few of the combinations of factors controlling these programmes yield a pattern, these patterns can be expected to have a yet undemonstrated adaptive value.