explique clairement et précisément : This finding inspired Jraissati and Douven (2018) to run a large online color-naming study among native English speakers, with the explicit aim of also covering the not fully saturated interior of CIELUV space. Their materials were the 1,332 Munsell chips represented in Fig. 1. They recruited over 1,800 participants, each of whom was shown a random selection of 65 chips and was asked to name the colors of these chips. A main research question Jraissati and Douven sought to answer was whether the BCTs—“black,” “white,” “gray/grey,” “red,” “blue,” “green,” “yellow,” “purple,” “pink,”, “orange,” and “brown”—are used with greater frequency for more saturated colors than for less saturated ones, which indeed turned out to be the case. Other results concerned the relation between frequencies of compound expressions (“baby blue,” “hunter green,” etc.) and saturation as well as the relation between saturation and consensus in naming. For our present concerns, however, Jraissati and Douven’s (2018) study is mostly important because it gives us an idea of the extensions of the eleven BCTs in CIELUV space. Fig. 4 shows a mode map of all the stimuli on the basis of BCT naming. Specifically, the left panel pictures each of the stimuli colored according to which pure BCT was most frequently used to name it. The right panel shows, for each BCT, the convex hull of the chips that were most frequently named by the BCT.2 If we think of the convex hulls shown in Fig. 4 as representing, at least approximately, the basic color concepts, then an interesting observation is that the concepts satisfy the earlier-mentioned convexity criterion almost perfectly, in that there are hardly any chips that had one BCT as their modal response but that lie in the convex hull associated with a different BCT. Arguably, together the basic color concepts as (approximately) presented by the convex hulls also give a fair coverage of CIELUV space: it is not as though we can make very fine distinctions in some parts of the space but then only crude distinctions in other parts. Thus, the system of basic colors concepts, supposing these to be given (more or less) by the structure shown in the right panel of Fig. 4, so far appears to satisfy at least two of our rational design principles: convexity and informativeness. In the following, the focus will be on other principles, notably, those having to do with the locations in a space of the various concepts’ prototypes: the principles of contrastiveness and representativeness. To verify whether these are satisfied by what, from Jraissati and Douven’s study, we may take to be our system of color concepts, it is not enough just to know which region in CIELUV space represents which color concept; we must also know the locations in that space of the prototypes. While there is some empirical work on color prototypes, this for the most part has the same limitations as Berlin and colleagues’ color studies, namely, the work was conducted using the selection of the most saturated Munsell chips shown in Fig. 2. And while prototypes may tend to be located toward the surface of the space, results reported in Douven, Wenmackers, Jraissati, and Decock (2017) concerning the blue and green prototypes suggest that it would be incorrect to hold that color prototypes lie always on the surface. Moreover, for gray and brown (sometimes described as a desaturated orange; e.g., Palmer, 1999, p. 141) we would not even expect to find the prototypes near the surface. The new study we conducted was aimed at locating more precisely the color prototypes in CIELUV space