Red-Green dichromats’ use of basic 
colour terms

We describe Red-Green dichromats’ use of basic colour terms and compare this with naming errors predicted by metameric equivalence derived from confusion lines in CIE (International Commission on Illumination) coordinates. After briefly reviewing previous work, the results from two tasks – prototype selection and colour term mapping – are presented. Dichromats’ choice of prototype was surprisingly similar to that of typical observers, especially for primary BCTs. More errors were made in the mapping task by including stimuli that were similar in transformed lightness and that shared a confusion line with stimuli that typical observers included in the range of the given term. Additionally, evidence was obtained that use of BCTs was dependent on residual R–G (red-green) mechanism activity.