This article reports an empirical study of the effects of interface colour (blue vs. grey) on ecommerce decision making. Participants viewed a set of products and information on the attributes of each and then made a series of purchase decisions that provided the basis for individual rankings of this set. Results support two proposed routes of influence. In the first, interface colour influences the cognitive capacities and strategies of consumers. This was evident as participants considered more attributes in the grey interface condition. Importantly, this was not mediated by participants' affective state. In the second, interface colour exerts influence via participants' aesthetic judgements. This was evident at a product-specific levelwith colour-related differences in product selection decisions mediated (for two product alternatives) by participants' assessments of product aesthetics. There was also some support for a product-generic effect of interface colourwith product aesthetics tending to be more influential in the grey condition. Overall, the results demonstrate the multifacetted nature of the influence of interface colour on consumer decision making in retail environments. (c) 2011 Wiley Periodicals, Inc. Col Res Appl, 2011;