From top to bottom: a1) V light curve with a fit of a long-term trend (dashed line), trend plus a 17 yr variation (full line), a2) V data difference from the long-term trend, showing the 17 yr variation from the fit, b) B − V,U − B color indices overplotted with the 17 yr variation, c) V − I_C color index overplotted with the 17 yr variation and d) effective temperatures of DM UMa between 1992−2007. See text for details.