Testing colour confusability among a new range of decimal stamps

Two experiments are reported in which the objective was to achieve minimal confusability among 14 colours required for the new lower-value range of decimal stamps. The main conclusion is that aesthetic considerations are largely incompatible with the criteria required to meet this objective. A symmetrically structured range of seven bright hues, each used at two levels of saturation, was found to have some advantages over an alternative unsymmetrical range which included more pleasing colours. This was mainly because the latter included greater variation along the brightness dimension, which produced large errors in recognition of darker hues. It could also have resulted from the greater nameability of colours made possible by combining hue and saturation cues systematically. The findings emphasise that absolute confusability of colour displays cannot be assessed reliably by viewing stimuli side-by-side, because this does not involve the imperfect mechanisms employed in colour recognition.