Observed and synthetic visual and near-IR colors of M-type AGB stars. Top panels: photometric variations for a sample ofobserved targets, derived from sine fits of light curves; near-IR data from Whitelock et al. (2000) have been combined with visual data from Eggen (1975) and Mendoza (1967); see Bladh et al. (2013) for details. Middle panels: photometric variations in the DARWIN models listed in Table 1, represented by loops, with colors calculated from sine fits of the light curves in the same way as for the observational data in the top panels. The lines are color-coded according to stellar parameters. Bottom panels: same model results, but color-coded according to pulsation amplitude. In all cases, the right panels show the same content as the left panels, zoomed in and centered on the color loops. The single-epoch photometric data shown in the background of all panels represent Galactic bulge Miras (Groenewegen & Blommaert 2005, gray dots) and field M-type long-period variables (Mendoza 1967, black crosses).