Edinburgh Napier University

  This paper is the first to establish the impact of colour on users' ability to interpret the informational content of concept diagrams, a logic designed for ontology engineering. Motivation comes from results for Euler diagrams, which form a fragment of concept diagrams: manipulating curve colours affects user performance. In particular, using distinct curve colours yields significant performance benefits in Euler diagrams. Naturally, one would expect to obtain similar empirical results for concept diagrams, since colour is a graphical feature to which we are perceptually sensitive. Thus, this paper sets out to test this expectation by conducting a crowdsourced empirical study involving 261 participants. Our study suggests that manipulating curve colours no longer yields significant performance differences in this syntactically richer logic. Consequently, when using colour to visually group syntactic elements with common semantic properties, we ask how different do the elements' shapes need to be in order for there to be significant performance benefits arising from using colours?