The semantics of colour terminology is a sadly underexplored domain within the discipline of translation studies. This situation is particularly noteworthy when it comes to focusing on idiomatic expressions in which colour words feature prominently. Despite the universalist hypothesis that colour categories are assignable to a general conceptuel system common to the human race, there still seems to exist a whole range of cognitive, perceptual and environmental factors with which the potential translator of colour-oriented idioms must grapple. Moreover, socio-pragmatic considerations tend to make the task even more forbidding. The aim of this paper is to demonstrate the untranslatability of colour idioms as far as English and Persian are concerned. [Source: abstract in book]