Because of their materiality, coloured marble columns played an important role in the architecture of the Late Republic and Early Imperial period, both as structural elements and as integral decorative features. The necessity and cost of importing these marbles, as well as the complex processing of the columns, made them a sign of prestige in both the surviving written sources and archaeological remains, and the most expensive element in architecture during the relevant periods. Two approaches have generally been employed to define the functions and aesthetics of coloured marble columns in architecture of these periods: the first approach analyses the roles of columns contextually, with regard to their technical and decorative properties. The second approach draws conclusions about the use and semantics of coloured marble columns through cross-genre comparisons which are then also compared to ancient texts. The uses considered appropriate in each context are significant factors in the choice of marble and indicators of social rank, as mentioned by ancient authors. The aesthetic and semantic properties of each kind of marble depend on its materiality, its display in architecture and its appropriate use, the perception of which was key for the ancient viewers’ evaluation. The number of coloured marble columns employed (alongside imitations produced in stucco) must have been considerably higher than we can observe in the archaeological record of the Late Republic, with the result that marble architecture and architecture imitating marble coexisted in townscapes and were thus perceived to be part of a common decorative system.