Maximum change observed in SpT to K_S− [W3], which is related to mass-loss (see text). The samples used here are the same as in Fig. 16, but we have represented only those stars observed on more than one epoch. The black cross represents the median uncertainties. The circles are CSGs from the SMC, the squares from the LMC. Left a): the colour indicates M_bol (derived from (J−K_S)). Right b): the colour indicates SpT.