In this article we present data comparing red-green dichromats' use of "Basic Color Terms" (BCTs) with that of standard trichromats. In a complementary article (Color Res Appl 2013) we use these data to evaluate two models of the mechanisms underlying dichromats' use of BCTs. There were three groups of observers-trichromats, protanopes, and deuteranopes-that each performed two tasks: "mapping" (which of these are exemplars of X?) and "best exemplar" (which is the best instance of X?), where X took the value of each Spanish BCT. The mapping task results were subjected to multidimensional scaling that revealed that dichromats differ from trichromats in the number and nature of the dimensions needed for describing BCTs' use. Trichromats required three dimensions closely related to the opponent color mechanisms (red-green, yellow-blue) and the light-dark channel. In contrast, tridimensional solution for dichromats was difficult to interpret, whereas the fit for the bidimensional solution was very good and revealed a chromatic dimension, which did not match any of the trichromatic dimensions, and an achromatic one. There were also some error-asymmetries (sometimes "A" was the predominant error when choosing exemplars of "B", but not vice versa) and the groups differed in the frequency of use of some BCTs (e. g., protanopes chose more stimuli as orange than trichromats and deuteranopes). As expected, the best exemplar task produced more correct responses than the mapping task, and for both tasks, "primary" BCTs (black, white, red, green, yellow, and blue) produced better results than "derived" ones (brown, purple, orange, pink, and grey). (C) 2013 Wiley Periodicals, Inc.