This article looks at the genre of casta painting developed in colonial Mexico during the eighteenth century. The genre consists of a series of paintings representing the different racial mixes that characterised New Spain throughout the colonial period and that continue to play an important role in contemporary Mexican society. By referring to several Foucauldian concepts such as disciplinary power, biopower, normalisation, deviance and heterotopia, this essay aims to locate the links between this genre and prevailing discourses on race, with a particular focus on the ensuing institutional and political practices implemented in the colony during this period. Centrally, by focusing on this genre as a representational technology of colonial surveillance, the paper argues that discourses on race in New Spain oscillated between an ideal representation of colonial society, ordered and stabilised through rigid classificatory systems, and a real miscegenated population that demanded a more fluid understanding of the colonial subject’s societal value beyond the limitations of racial determinism