A plethora of theories and studies exist that focus on the relationship between colour and esthetic response as well as the construction of colour harmony. However, consensus regarding colour harmony is lacking in the literature leaving designers and architects with colour harmony information that is contradictory and ambiguous. This article examines both early and more recent theories and definitions of colour harmony. The diverse theoretical paradigms and disparate assumptions embedded within these theories are discussed in some depth, and the validity and veracity of predictive colour harmony theories are discussed from a current theoretical perspective. An updated definition of colour harmony is provided along with a conceptual model that represents an attempt to revise colour harmony in line with current theoretical paradigms. This conceptual model acknowledges that the interface between colour and esthetic response is less deterministic and predictable, and more idiographic than previous theories allow. In addition, the conceptual model suggests that colour harmony is contingent on factors that may influence the relationship between colour and esthetic response such as individual and cultural differences as well as perceptual, contextual, and temporal factors. (C) 2010 Wiley Periodicals, Inc. Col Res Appl, 35, 267-273, 2010; Published online I March 2010 in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/col.20578