Colour–magnitude diagram (absolute K_s band magnitude vs. dereddened colour ) for the theoretical models (grey points) and our data (in colour). The colour indicates the derived extinctions from the RJCE method. We cut some stars that are not compatible with the theoretical models, as can be seen in the inset plot (which is the same, but extending to bluer colours). The colour scales are different in the two plots and the rare stars have spuriously high extinctions of up to about 2 mag in the K_s band.