Observed and synthetic visual and near-IR colours. Top panel: synthetic phase-averaged colours from wind models where the dust temperature is determined by radiative processes (red squares) and the gas temperature (blue squares). Bottom panel: photometric variations derived from sine fits of observed light-curves for a sample set of M-type miras. The synthetic photometric variations for the models marked with filled squares (M = 1 M_⊙, L = 5000 L_⊙, T_∗ = 2800 K, u_p = 4 km s^-1 and log n_gr/n_H = −15) in the top panel are also plotted (solid red and blue loops). The colours are calculated from sine fits of light-curves, same as for the observational data. See Bladh et al. (2013) for more details concerning the sine-fit of observed light curves. For details on the observational data see Fig. 5.