In a pioneering set of experiments, Rosch investigated the colour processing of a remote traditional culture. It was concluded that colours form universally natural and salient categories. However, our own cross-cultural research, backed up by neuropsychological data and interference studies, indicates that perceptual categories are derived from the words in the speaker's language. The new data support a rather strong version of the Whorfian view that perceptual categories are organized by the linguistic systems of our mind.