Chromaticity areas (CAs) corresponding to the convex hull of chromaticity coordinates calculated from the metamer sets reconstructed from 10 <i>ρ</i>_RGB responses of the different colour samples in Fig 1 recorded with an RGB camera.

<p>A. Panels correspond to each one of the seven different colour pairs used in our experiment; colour difference values (ΔC) between the pair members are included on each panel. Shaded areas correspond the the CA’s for each colour sample in a sample pair and their intersection represents the confusion region (ARC) expected for a given sample pair. Chromaticity coordinates calculated from measured reflectance spectra are indicated by the (*) and (●) markers. Ellipses represent MacAdam’s [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0125817#pone.0125817.ref048" target="_blank">48</a>] (blue) and Newhall [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0125817#pone.0125817.ref050" target="_blank">50</a>] (green) colour-difference thresholds calculated for the chromaticity coordinates obtained from measured spectral data. Both ellipses are drawn at their actual scale. B. Regions in the 1931 CIE Chromaticity Diagram covered by the <i>x</i> and <i>y</i> axis of the panels in A. Variations in area size are due to differences in scale required for plotting the two colours making up each sample pair.